A yet-another-how-to-delete-stubborn-files tip, but not one I've seen mentioned here.
I was downloading a file with Interarchy, and for some reason, the download failed (I forget why now). I was left with an incomplete file, and several days later I got around to trying to delete it. I got a message when I tried to move it to the Trash that said "The item "filename" is being used by another task right now. (Other tasks include moving, copying, or emptying the Trash.)"
Well, I wasn't doing any of those things, and I had logged out and restarted several times in the interim, so I was sure no process had it open. I looked at the attributes with /Developer/Tools/GetFileInfo, and it showed a file type of 'bzy '. That looked a lot like the word "busy", so on a whim I changed it to something else (using SetFile -t "blah" filename), and was then able to move it to the Trash with no problem.
I gather that this special file type is particular to the Finder, not to Interarchy, since I tested this case on another file, with similar results. However, Apple Help doesn't seem to have anything about this in it, and searching Apple's Knowledge Base insists that I must be searching for "bay" instead of "bzy ", and returns irrelevant results. Anyone else know anything about this file type?
[Editor's note: I tested this by using "touch" to create an empty file, then "SetFile" to change it to "bzy ", and sure enough, no deletion or moving was possible. Changed it to anything else, and off it went to the trash.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020920055805577