If you are not getting the details of the error try to enable the Custom errors so that it will display the stack trace..
Here are the steps:
1) Navigate to the web application’s web.config file
2) Find the SafeMode setting:
<SafeMode MaxControls="200" CallStack="true" DirectFileDependencies="10" TotalFileDependencies="50" AllowPageLevelTrace="true">
3) Find the CustomErrors setting:
<customErrors mode="On" />
and set mode=”Off”:
<customErrors mode="Off" />