500 Error when Admin IP is unlocked

I wanted to try if the plugin also locks out an IP when the ThemeMyLogin sidebar widget is used to log in, which by the way it does. Fine so far, i then entered my email address to get the reset link, clicked it and got a 500 Server error. I tried in a different browser to refresh the page and the unlock worked, just something triggered the error.

Here´s all I can tell you abou the error:

Server: Linux
WP: 3.5.1
Plugin: 3.6.7
Browser one (used to trigger the block): Firefox
Browser two (used to release the block): Chrome

The Error said:

The website encountered an error while retrieving http://www.mydomain.com/?_wfsf=unlockAccess&key=BLABLABLA&func=unlockMyIP.
It may be down for maintenance or configured incorrectly.

Here are some suggestions:
Reload this webpage later.

Well that´s nothing I need on a daily basis but maybe put it on the maintenance list.

http://wordpress.org/extend/plugins/wordfence/