I didn't get any error messages at all, just blank pages. I "fixed" the issue by renaming the securitycheck_spam_protection folder in /plugins/system/, which then allowed me to load my website and get into the admin console.
Umm, it's odd. Sounds like a not defined function or similar.
i would need access to your error.log (or administratve credentials for cpanel and Joomla backend) to check what's happening. If you are agree please use the email from which you receive forum notifications to send me them.