Error: A copy of ApplicationHelper has been removed from...

Hello.

I just started getting this error but can't figure out what I did in the
past day that might be causing this:
"A copy of ApplicationHelper has been removed from the module tree but
is still active!"

Apparently, there are others that have seen this -- gathering from a
google search -- but I can't find any solution.

Has anyone seen this? Here is what I've done recently:
1. Added ssl plugin
2. Added a couple authorize.net ruby code to my lib/ dir:
http://developer.authorize.net/samplecode/

Thanks.