G5 sleep and wake disorder

[cgnrs]

My G5 2.7 dual core (3 GB RAM, 1 PCI card) froze up after I inadvertently hit the keyboard while iTunes and iViewMediaPro were in use (others have described the same phenomenon in forums). After restart a "No" or "Prohibited" sign appeared on the grey screen above the spinning wheel. A second restart brought the computer back to life, but since then it can't be put to sleep - when I try to put it to sleep, the interior fans in front of the CPU cooling unit continue to run and speed up after a couple of minutes until they reach maximum rpm. Plus, the machine won't wake up from sleep. A quick emergency restart typically results in a complete reboot, but if the machine is shut down overnight, the "No/Prohibited" sign will appear first, and only the next shut down and restart is successful. I have pretty much tried all remedies I could find mentioned online: repaired permissions, re-set PRAM, optimized the system, rebuilt and replaced directory, installed a new System Folder, re-set PMU button, wiped one disk clean and installed a completely new system. The Hardware Test repeatedly produced one error code after a few seconds: 2STH/1/3: DRIVE BAY, but the test also came back several times with no errors indicated when the machine had cooled off. I concluded the error message had something to do with the operating temperature.

This is the system log from the successful second start-up this morning:

Jul 22 07:48:15 localhost kernel[0]: standard timeslicing quantum is 10000 us
Jul 22 07:48:14 localhost memberd[43]: memberd starting up
Jul 22 07:48:15 localhost kernel[0]: vm_page_bootstrap: 762763 free pages
Jul 22 07:48:14 localhost mDNSResponder-108.6 (Jul 19 2007 11: 33:32)[36]: starting
Jul 22 07:48:15 localhost kernel[0]: mig_table_max_displ = 70
Jul 22 07:48:15 localhost kernel[0]: 105 prelinked modules
Jul 22 07:48:15 localhost kernel[0]: Copyright (c) 1982, 1986, 1989, 1991, 1993
Jul 22 07:48:15 localhost kernel[0]: The Regents of the University of California. All rights reserved.
Jul 22 07:48:15 localhost lookupd[45]: lookupd (version 369.5) starting - Tue Jul 22 07:48:15 2008
Jul 22 07:48:15 localhost kernel[0]: using 7864 buffer headers and 4096 cluster IO buffer headers
Jul 22 07:48:15 localhost kernel[0]: DART enabled
Jul 22 07:48:15 localhost kernel[0]: USB caused wake event (EHCI)
Jul 22 07:48:15 localhost kernel[0]: FireWire (OHCI) Apple ID 42 built-in now active, GUID 001451ff fe111646; max speed s800.
Jul 22 07:48:15 localhost kernel[0]: CSRHIDTransitionDriver:robe:
Jul 22 07:48:15 localhost kernel[0]: CSRHIDTransitionDriver::start before command
Jul 22 07:48:15 localhost kernel[0]: Security auditing service present
Jul 22 07:48:15 localhost kernel[0]: BSM auditing present
Jul 22 07:48:15 localhost kernel[0]: disabled
Jul 22 07:48:15 localhost kernel[0]: rooting via boot-uuid from /chosen: F55225C6-0B32-3022-AC41-A53B5927CF0E
Jul 22 07:48:15 localhost kernel[0]: Waiting on <dict ID="0"><key>IOProviderClass</key><string ID="1">IOResources</string><key>IOResourceMatch</key><string ID="2">boot-uuid-media</string></dict>
Jul 22 07:48:15 localhost kernel[0]: Got boot device = IOService:/MacRISC4PE/ht@0,f2000000/AppleMacRiscHT/pci@7/IOPCI2PCIBridge/k2-sata-root@C/AppleK2SATARoot/k2-sata@0/AppleK2SATA/ATADeviceNub@0/IOATABlockStorageDriver/IOATABlockStorageDevice/IOBlockStorageDriver/Hitachi HDS724040KLSA80 Media/IOApplePartitionScheme/Untitled 3@3
Jul 22 07:48:15 localhost kernel[0]: BSD root: disk0s3, major 14, minor 3
Jul 22 07:48:15 localhost kernel[0]: CSRHIDTransitionDriver::stop
Jul 22 07:48:15 localhost DirectoryService[56]: Launched version 2.1 (v353.6)
Jul 22 07:48:15 localhost kernel[0]: IOBluetoothHCIController::start Idle Timer Stopped
Jul 22 07:48:15 localhost kernel[0]: Jettisoning kernel linker.
Jul 22 07:48:15 localhost kernel[0]: Resetting IOCatalogue.
Jul 22 07:48:15 localhost kernel[0]: Matching service count = 0
Jul 22 07:48:15 localhost kernel[0]: Matching service count = 5
Jul 22 07:48:15 localhost kernel[0]: Matching service count = 5
Jul 22 07:48:15 localhost kernel[0]: Matching service count = 5
Jul 22 07:48:15 localhost kernel[0]: Matching service count = 5
Jul 22 07:48:15 localhost kernel[0]: Matching service count = 5
Jul 22 07:48:15 localhost kernel[0]: IOPlatformControl::registerDriver Control Driver AppleSlewClock did not supply target-value, using default
Jul 22 07:48:15 localhost kernel[0]: IPv6 packet filtering initialized, default to accept, logging disabled
Jul 22 07:48:15 localhost kernel[0]: UniNEnet: Ethernet address 00:14:51:11:16:46
Jul 22 07:48:15 localhost kernel[0]: AirPortPCI_MM: Ethernet address 00:11:24:a5:a2:50
Jul 22 07:48:15 localhost launchd: Server 4107 in bootstrap 1103 uid 0: "/usr/sbin/lookupd"[45]: exited abnormally: Hangup
Jul 22 07:48:15 localhost diskarbitrationd[42]: disk1s3 hfs AA27BFA1-7ECE-3734-BF53-59265C5B89DD G5 disk 2 /Volumes/G5 disk 2
Jul 22 07:48:16 localhost diskarbitrationd[42]: disk0s3 hfs F55225C6-0B32-3022-AC41-A53B5927CF0E G5 disk 1 /
Jul 22 07:48:16 localhost kernel[0]: Registering For 802.11 Events
Jul 22 07:48:16 localhost configd[40]: WirelessConfigure: 88001003
Jul 22 07:48:16 localhost kernel[0]: [HCIController][setupHardware] AFH Is Supported
Jul 22 07:48:16 localhost configd[40]: initCardWithStoredPrefs failed.
Jul 22 07:48:16 localhost configd[40]: WirelessConfigure: 88001003
Jul 22 07:48:16 localhost lookupd[71]: lookupd (version 369.5) starting - Tue Jul 22 07:48:16 2008
Jul 22 07:48:18 G5 kernel[0]: UniNEnet::monitorLinkStatus - Link is up at 100 Mbps - Full Duplex
Jul 22 07:48:18 G5 configd[40]: setting hostname to "G5.local"
Jul 22 07:48:20 G5 kernel[0]: ATY,ChockStone_A: vram [a0000000:10000000]
Jul 22 07:48:20 G5 kernel[0]: ATY,ChockStone_B: vram [a0000000:10000000]
Jul 22 07:48:20 G5 /System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow: Login Window Application Started
Jul 22 07:48:20 G5 launchd: Server 0 in bootstrap 1103 uid 0: "/usr/sbin/lookupd"[71]: exited abnormally: Hangup
Jul 22 07:48:20 G5 configd[40]: executing /System/Library/SystemConfiguration/Kicker.bundle/Contents/Resources/enable-network
Jul 22 07:48:20 G5 configd[40]: posting notification com.apple.system.config.network_change
Jul 22 07:48:20 G5 lookupd[79]: lookupd (version 369.5) starting - Tue Jul 22 07:48:20 2008
Jul 22 07:48:21 G5 loginwindow[74]: Login Window Started Security Agent
Jul 22 07:48:23 G5 mDNSResponder: Adding browse domain local.
Jul 22 07:48:24 G5 configd[40]: target=enable-network: disabled
Jul 22 07:48:25 G5 /System/Library/Frameworks/ApplicationServices.framework/Frameworks/ATS.framework/Support/ATSServer: ATSServer: FODBVerifyReviveResults made adjustments

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The machine functioned without fail for 3 years. Has anyone had that kind of crash and found the remedy for it? Is there anything that can be done short of sending the machine to Apple for repair? I am thankful for any expertise, input, help, advice.