I'm trying to create a form in InfoPath 2007 with some managed code (C#) in
the validation event. As soon as the managed code project is created, I get
the following message when trying to open an instance of the form :

"InfoPath cannot open the selected form because of an error in the form's
code.
Policy settings prevent opening Internet forms with managed code. To fix
this problem, contact your system administrator."

When I try to preview the form from the design view, I just get the message
"InfoPath cannot open the selected form" without any additional information.

I already did/tried the following:
- Checked if the dll's (both debug and release) had unrestricted permissions
- Removed all restrictions for the different zones in the setting for the
.NET framework
- Elevated permissions in the IE settings as much as possible
- Disabled the form option for browser compatibility
- Publish the form to another location

I couldn't find any policy settings that gave me the impression that they
had anything to do with the managed code.

Version are Office 2007 Ultimate and Vista Business

Does anyone have any suggestions?