Don't know? Are you out of space on your hdd? How could your folder not hold any more files? I'm probably missing something, but defrag your hdd. Clear the files you have queued to d/load, and try running
CCleaner.com, to free up some space on your hdd.
Tip: Purge the Downloads Queue!
Delete your LW prefs whilst LW is closed:
Fixes for Limewire when LW isn't operating as it should!