Multi-application Slowdown

[cmbello]

I am running OSX 10.2.8 on a powerbook G4 and have recently acquired a problem running basic mac applications such as mail, calendar, stickies, preview... I can open the programs and usually manipulate things within the first window (I can receive and read e-mail for example) but if I try to do anything with the drop down menu (quit, compose, reply) the application gets stuck in thinking mode and usually requires a force quit. I can avoid some of this using shortcut keys, but it really hampers my computer use. I have not added any software or made any changes that seem likely to cause such a problem. Other, more complex applications are unaffected (office, adobe, explorer, etc.) Disk utilities and first-aid software have not solved the problem. I have been advised to back-up, erase and re-install the operating system, but before I do that I was curious if others have encountered this problem and if doing so would actually be the best fix. Would appreciate advice.

thanks,
Courtney