The itunes application could not be opened. an unknown error occurred (1301
"The itunes application could not be opened. an unknown error occurred (13014)"
An archived tip on the iTunes for Windows forum that suggested deleting the iTunes Library Genius.itdb. That didn't work, I also had to delete iTunes Library Extras.itdb. (For the record I renamed them instead of deleting, but the original post suggested deleting).
Anyway, I thought I'd pass that on in case anyone else experiences this problem.
iBook G4, Mac OS X (10.5.8)