That is a question for the programmers.
I would assume that LimeWire couldn't move it b/c the file is corrupt. It seems that one of the latest inhancements to the program is file verification..
After adding all the illegal characters to my filter exceptions I am still encountering files that cannot be moved to the library. I don't believe that illegal characters are the problem after all. I'm thinking it probably has to do with LimeWire's file verification routines.

Back to square one. I'm going to try to use an earlier version of LimeWire to see if this is true.