There are cases where I get the dreaded error message telling me:
"An error occured. Try this action again. If the problems continues, check the Microsoft Dynamics CRM Community for solutions or contact your organization's Microsoft Dynamics CRM Administrator. Finally, you can contact Microsoft Support."
When there are no errors in the server Event Log usually you have to resort to running a trace and then sifting through the huge text file to find the error. However, Fiddler can give you the error without having to be on the server and without having to sift through huge text files for one line of an error message.
Start up Fiddler, reproduce the error and then I typically look at the timeline, that shows a big error symbol. Double click on that symbol and you'll see the error you couldn't otherwise see.
Something rather simple but can make troubleshooting that much faster.
Dynamic Methods Inc.