I've used this plugin on many blogs, but recently I had to deactivate it on one site when I was doing a redesign -- and now the plugin will not activate. It times out and then gives a Internal Error 500.
I've spent hours trying to see if it was an issue related to .htaccess and other possibilities. But it seems that it is actually an issue with the plugin and the Xavisys forum indicate that -- because this is a free plugin -- the author has no plans to update the plugin at this time.
It's too bad. This is the best related plugin I've every used. If you can get it to activate, don't deactivate it. You may never get it started again... :(