I'm suddenly getting the error :EntityMetadataWrapperException
Your site has not been running on Drupal 7.21 for several months. You have recently upgraded.

There was a security fix in the drupal core image module in 7.20 which broke several contributed modules. 7.21 has a new variable to mitigate the problem, but if your issue involves images, it is probably related to the security fix. For more information read the release notes.