Whitescreen When posting comments

On my site http://www.401kplanning.org I am using the latest version of WP and all plugins are up to date. I recently noticed that when trying to post a comment, a white screen appears and the comment does not register.

Using advice from earlier posts on the forum, I turned off/on plugins and isolated the Akismet plugin as the culprit: with Akismet active, white screen appears when comment post is attempted; with Akisment deactivated, no problem. Obviously, a pretty important plugin to be without.

Anyone else faced this? Any solutions or suggestions.

Thanks