there is a some improvement in sharepoint 2010, when the error occurs, the error message is still very short, but it will show you the correlation ID, which is the GUID that which is automatically generate by the sharepont web server upon each request.
you can use this correlation ID and go into the sharpeoint Log to find out which the root cause of this error.
here is the path of Shareoint LOG
C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\LOGS
Open the Log File and Search it with Correlation ID
for more detail Information how to find this new trouble shooting in sharepoit 2010
there is a post from Dina Ayoub Program Manager on SharePoint, MSFT
http://sharepoint.microsoft.com/Blogs/GetThePoint/Lists/Posts/Post.aspx?ID=353