Recenlty a client had published a SharePoint site through TMG. Everything looked great until you went to view/edit the properties of a document in a document library. I got the following error:
“Error Code: 500 Internal Server Error. The request was rejected by the HTTP filter. Contact the server administrator. (12217) ”
Trying the same actions on any other list/library worked fine; just not for a document library.
The problem turned out to be related to HTTP filtering in TMG.
To fix the issue, Open the properties of the firewall policy. Click Filtering > Configure HTTPunder the Traffic tab.
Uncheck Verify normalization.
Save and apply changes and you should be all set.
But in case your problem is related with the people picker you should uncheck the value “Block high bit characters.” This will fix the problem. This problem also happens when you publish the OWA urls thorugh TMG or ISA
Hope that helps!
Albandrod's Memory 