Fields not remembering values?

So this first happened with the Twitter module, but I'm now having the same issue with the Authorize.Net Payment Webform module.

With the Twitter module I would put in the Twitter username and password, but it would not retain the values once it was saved, and thus would not post to Twitter.

Now with the Authorize.Net Payment Webform I am entering the API key and transaction key, but once i hit 'save' it does not seem to retain the entered values, and thus does not work.

Any ideas as to what might be causing this?