Comment 1 for bug 495181

Thank you for catching this. The symbol F is commonly used for both the Farad and the Faraday constant, and the Faraday constant was registering itself as F and overwriting the farad. This can't be allowed to happen, so I added a check to make sure that previously registered units can not be overwritten. It's fixed in the trunk.

I'll try to get a new release out as soon as possible.