I found this issue recently–at first I thought it was just my environment, but have confirmed it on a couple of different environments. When you are on a Win 7 box (and probably R2 as well), in GPMC and viewing the setttings of a GPO that had previously been created and contains software restriction policies, you will get an error when GPMC tries to display those SRP settings. Specifically, the error looks like this:
|Software Restriction Policies
Software Restriction Policies/Security Levels
Software Restriction Policies/Additional Rules
|The following errors apply to all of the above settings:|
|An unknown error occurred while data was gathered for this extension. Details: Unable to cast object of type ‘System.String’ to type ‘Microsoft.GroupPolicy.Reporting.Extensions.Registry.UnknownType’.|
From the looks of it, it appears to be a bug in the way the Win 7 GPMC object model is parsing these settings. I’ve reported it to MS but wanted to let everyone know about it so you don’t think you’re going crazy. Not surprisingly, if I open the GP Editor on this GPO, all of the SRP settings appear fine. This is only an issue with the GPMC reporting of settings.