Seeing many of those “descriptive” SharePoint errors like this one lately:
The "MyWebPart" Web Part appears to be causing a problem.
Web Parts Maintenance Page: Use this page to temporarily disable Web Parts or remove personal settings.
Troubleshoot issues with Windows SharePoint Services.
If you want to see more meaningful error description, do a simple trick. Change the following line in your SharePoint web.config into something like this:
> <SafeMode MaxControls="50" CallStack="true">
Of course, make sure NOT to change this switch in your production environment, as it could reveal potentially sensitive information.