DVD-RAM & Retrospect 5.1 trouble

[morfeo]

Hi everybody,
I have a problem with some DVD-RAM cartridge that I use for back-up data with Retrospect 5.1. Recycling media some disk results impossible to initialize with Retrospet (-102 trouble communicating) but also with the OSX Disk utility (disk in use) and furthermore I can't eject the disc (-36)! The only way I found is hardware eject at restart. I've tried Norton, Disk Warrior, Drive 10 to fix the problem but no success. I figure that the problem is the file from Retrospect (or something retrospect wrote) that I can't delete.
Any Idea about how initialize the disks or delete the file?

Thanks all,

Morfeo