itunes 7.0.2 and system update not working?

[wizerd]

i've got an imac G5, and was running itunes 6 which worked fine... when i downloaded itunes 7.0.2, it seemed to install correctly, but upon opening the application, I clicked the agree thing that pops up the first time you use itunes... and this pops up...

"The iTunes application cannot be opened. An unknown error has occurred (-50)"

so i reinstalled it, redownloaded it and reinstalled it, installed an updated version of quicktime.... i was going to do a whole software update but the connection timed out? I'm on cable, ran network diagnostics, and everything was fine... so maybe that's my problem? i can't figure that out either...

i have no clue... i was gonna just delete itunes and put my old version back but it has an autodetect version thing on the installer that won't let me do that even after it's deleted and cleared?

anybody with any ideas whatsoever let me know asap...