This is a very specific hint, but maybe it will help somebody.
If you are upgrading from OS 9.2.2 to OS X 10.2, and you have files with Arabic names, every file which has the Arabic letter Hamzah in its name will not be editable. You will see these files when you navigate with the OS X Finder, but you can not open them either with TextEdit nor, strangely, with Nisus under Classis mode. Also you will not be able to copy them, rename theme or even delete them.
Solution: Don't panic, the files are there. You have to boot from OS 9 and there you need to rename them so that the letter Hamzah should not be used. I think it is because the font Lucida doesn't translate this letter correctly.
[Editor's note: Can anyone confirm this glitch?]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20021206051810347