Debugging Sharepoint

Try the event viewer to see if Sharepoint as left any tell tale signs.

and also

12 Hive:


C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\LOGS

In the web.config for the application:

Normally found in the C:\Inetpub\wwwroot\wss\Virutal Directories\

Where is equal to the port number your sharepoint site is using.

In the web.config you can enable the debug settings, like you can for asp.net applications, this is a great help as normally sharepoint will only output the message "Unknown Error" hiding the .net exception, leaving you guessing!