What platform are you using? Are you putting it into the XBMC\plugins\programs folder? Try out these locations
If you're still getting errors, turn on debugging in System Settings and try installing again. Then upload the contents of xbmc.log to a pastebin site. Details are in my signature.
When posting about a problem please submit a debug log to give you the best chance at getting an answer. It's easy, painless, and helps provide necessary information.