Are you already using ULSviewer tool? Great! If not, please download your copy from the following site:
It is an excellent tool to read error messages from the SharePoint logs. You may have noticed that SP 2010 throws an error with correlation ID which is meaningless for the users. It doesn’t tell anything to the user about the error. You can use ULSviewer to search the error in the logs using the correlation ID. Error log gives you complete description of the error.