Product:
Cognos BI 10.1.1 office
Windows 2008 R2 server
Microsoft Excel 2007

Symptom:
Error message when you import a report with prompts to excel.

Part of Error message:
Client found response content type of (text/ type / HTML) but expected
(text/xml).
…
DOCTYPE html PUBLIC “-//W3C/DTD XHTML 1.0 Strict//EN”
…
500 – Internal server error.
…
There is a problem with the resource you are looking for, and it cannot be displayed.
…

Solution:
On you Cognos BI gateway server
Start Internet Information Service Manager
Expand the Default Web Site so you see cgi-bin folder
Click on application cgi-bin
Double-click on icon Error Pages.
Click on the right side on “Edit Feature Settings”
Mark “Detailed errors”
Click OK

Test again – you do not need to restart the IIS to active the change.

The error in GO OFFICE happen when “Detailed errors for local requests and custom error pages for remote requests” is marked in the IIS dialog.