Nah... I get them almost every time i restart, too. They're often assosiated with drag'n'drop operations over network or several Volumes (disks) last time you were logged in. Dreamweaver is another culprit, specially when you use the ftp function, so is Cyberduck (do you see a pattern here?
).
Clipboard also seems to generate them...
I don't worry too much, this was normal behaviour under OS 7-9, and I've actually kind of missed it under 10.2 and 10.3...
I think there was an Apple Support article that explained why this happened, but I don't seem to be able to find it right now... Edit: There was also lot of discussion on the apple support forums but all references to "the" thread about the subject seemed to be broken...
Remembered another common culprit: Windows Media Player... (maybe it will get better now that I've deleted that and installed flip4mac).