..even curiouser
I have the same issue. All the problem files are ex windows files that I put onto my ipod for transfer to mac, particularly "my pictures" and "my music". So this all relates to folders on the ipod itself.
I can delete sub folders in my pictures, but cannot delete the file. I tried all the suggestions above but no result. After using the terminal option and trying to transfer my pictures to trash, I get the message "my pictures is locked. do you want to tranfsfer anyway?". Select yes, get the sound of the file moving but nothing happens. The file has not moved.
Even stranger, the trash is empty when the ipod is not plugged in, but once it is mounted several files that I did manage to send to the trash appear in the trash again and cannot be emptied. Once the ipod is ejected, the files dissappear from trash only to reappear when the ipod is next connected.
This is very annoying as prior to this, the only two things I regretted about switching were (1) not doing it sooner, and (2) getting the base model MBP instead of spending money on a larger hard drive.