Offline Credit Card Module trouble after upgrade to v. 1.3

[mfitz]

I'm having some trouble getting Kevin Klika (Ox40)'s great offline credit card module (v2.0.5) working after upgrading our shop to PS v1.3. There's probably a simple fix, but I have no idea what it is.

After installing and enabling the module, I get this error when trying to checkout with a credit card:

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Kevin suggested to another user with the same problem that he enable error reporting to figure out what's happening, but I'm not sure how to do that.

Any suggestions?

Thanks!