I can confirm that this is a problem with 2.7.3 under Windows 2000. The save directory exists and has full access for "Everyone", and so does the Incomplete directory, but when trying to download a file, "Could Not Move To Library" is immediately returned.

Note: This only happens for files that contain non-US ASCII characters in the name, like ***************.mp3", which is displayed as (note the incorrect display) *******************.mp3".

The problem seems to occur with EVERY file name that isn't in US ASCII.
This was no problem with earlier versions of LimeWire.