Well using the magnet link I gave, it can potentially give speeds of over 200 KB/s. So if you're only getting around 40 & the maximum of all other downlds is around 40 KB/s then something is wrong. Either the isp is shaping p2p or ... ?

You can try deleting your LW prefs folder whilst LW is CLOSED only. Found here /Users/your_username/Library/Preferences/LimeWire

But make a note of important settings because you'll need to reset them next time you open LW. That includes changing the days to keep incomplete files to larger than the default 7 days.