plug-in trashed my site?

I tried to install a Twitter plug-in on my site. I guess I had already installed it, but not activated it. I am now not allowed to un-install it, or to do anything else for that matter, including creating a new post. I get the following message:

“Fatal error: Cannot redeclare aktt_widget() (previously declared in /home/.liebling/*my name* / *my site* /wp-content/plugins/twitter-tools/twitter-tools.php:981) in /home/.liebling/*my name* *my site*/wp-content/plugins/twitter-tools/twitter-tools.php on line 981

Any ideas?