Your site is running Beta 4. The current, much more stable release is Beta 7. I cannot say whether it will fix this particular error, but there is no logic to the error you posted. It suggests that a particular wrapper function is not used in a place where it definitely is.
Please PM the full error message to me so that I can look into it more closely. The error may have security implications for your site, so I have removed it from the post above.