I'm assuming that you're trying to move your files WHILE the LW is still running, in which case, this is most likely a memory leak issue. 2.2 & 2.3 (that I know of) had this problem where once LW runs it starts eating up all the RAM available. This has been fixed in 2.4 which is available now.

So you might want to try an upgrade. 2.4 is far more stable than the previous versions.

Hope this helps.