Fundraising plugin not working, also adds error text above site's header

Only a few hours into WPMU dev, already having issues. Sweet.

Have only installed one plugin so far: fundraising. As soon as I installed the plugin, it inserted error code above the header of my site. This is the text: "Warning: session_start(): open(\xampp\tmp\sess_icqr25mtvusjuodrs1mgnbb7a2, O_RDWR) failed: No such file or directory (2) in S:\htdocs\sitename\wp-content\plugins\fundraising\fundraiser.php on line 686"

Also, installing this plugin caused my WP dashboard to become PAINSTAKINGLY slow. All WP function was fine until I installed this plugin. Now, any command (add post, add media, settings, etc.) in the WP dashboard takes 2-3 minutes and in most cases simply times out. (It took me about 10 minutes just to uninstall this plugin) Once I uninstall the plugin, my WP dashboard is no longer slow and the error code is gone.

Um... am I missing something here? I've installed hundreds of plugins on a dozen of WP sites and I've never had a plugin do this.