500 Error – Internl Server Error

I was running WP 2.7 and it was working fine up until about a month ago. Then when a new user tris to register when they click the “Register” button they will get a “500-Error – Internal Server Error”. I have a plug-in wp-recaptcha and thought it was it. So, I deactivated and deleted the plug-in, still get the error. Then I decided to update to the lates WP 2.7.1. Just got through with it, did not load any plugins and I still get the “500-Error – Internal Server Error” when trying to register a new user. What’s so strange is the user regeristing still gets and email and can still login. It’s just the wp-login.php (I assume) that is getting the error. I have checked with the hosting provider and say it’s the program. Anyone have any suggestions?