Try the following in order:

1. Login as admin or host and re-visit the module. You may see a more detailed error message.

2. While logged in as admin or host check Admin-->Event Viewer to find a more detailed error message and stack trace.

3. If you are able to use debugger (VWD, VS2003, VS2005 as available and appropriate for DNN version), set break point inside the Catch statement of the Try . . . Catch block within your module's Page_Load event handler, then examine the exception's Msg and other properties.

4. Set a break point on the first executable statement of the Page_Load event handler and step through the code line by line, etc.

5. If the breakpoint set on the first statement of Page_Load is not being hit before the error is thrown, the problem most likely lies within the .ascx markup code.  Usually you can spot these on close examination. In a few tough cases, I've had to comment out sections of the .ascx markup code (and any lines in the code file/code behind that references a commented out server control). to isolate the problem area.