After unsuccesfull modinstall an IIS error

Hello

I have installed my PunBB forum today, and configured it succesfully. Also I installed a skin without problems.
After that I tried the Calender, Poll, and Attachmentmods.

None of them did work because my PunBB version was too new. But now I have got the following errormessage:

IISPassword
The page cannot be displayed 
There is a problem with the page youare trying to reach and it cannot be displayed. It is most likely that configuration files for this url are corrupted. 

--------------------------------------------------------------------------------

Please try the following:

Click the Refresh button, or try again later.
Open the home page, and then look for links to the information you want.
If you believe you should be able to view this directory or page, please contact the Web site administrator by using the e-mail address or phone number listed on the home page.
HTTP Error 500
IISPassword for Internet Information Services 

Other forums on my webhost work without problems.

How can I solve this problem without reinstall everything?
Thanks in advance,
Dr. Ir. Kevin