Whilst doing some troubleshooting work for a client’s group policy settings that were not being applied to a vista machine I launched the Group Policy Management Console (gpmc) and when I went to view the Resultant Set Of Policy (RSOP) of a client machine and when I tried to view the default domain policy I received the message “An error occurred while generating report: An unknown error occurred while the HTML report was being created.” All other group policies appeared fine – it was just the default domain policy – arguably the most important one and not an easy one to restore. My first step was to use a DC that did not have the gpmc installed to use the native group policy tools within the Active Directory Users and Computers snapin. Fortunately this tool worked and I could see the settings…..lots of them.
As I knew the group policy did not seem to be corrupt I then went back into gpmc and attempted a backup of the group policies. All but the default domain policy backed up successfully.
The error message almost looked similar to issues when trying to view web pages on a server with the enhanced ie security enabled but it didn’t really make sense that it was only affecting one group policy.

After a few minutes of digging I found an entry on tek-tips (a site I don’t like to use due to the popups and nag screens) but in this case the answer worked. From Roadki11’s posting on tek-tips.com:-

Cause:
Seems to be something with importing IE security settings.

Solution:
Edit install.ins inside: {GUID of Policy}\user\MICROSOFT\IEAK

[Security Imports]
ImportSecZones=1

Set it back to “0”

Using gpmc I obtained the guid of the policy by right clicking the policy and choosing properties then I connected to c:\WINDOWS\SYSVOL\sysvol\domain\Policies\{guid}\user\Microsoft\ieak
First I made a backup and then edited install.ins, set ImportSecZones to 0 and was then able to edit the policy in gpmc.
Hopefully the background information and the instructions on how to connect to the correct file helps others.
Whilst you are in the gpmc make sure you go down to Group Policy Objects, right click, Backup All, select a location, enter the date and time stamp for the description and back those policies up. Document where the backups are stored so that if you need to restore them they are easily accessible – even on another computer.
I’ve now added the backup to our checkup and system documentation instructions so at a minimum we will have monthly backups of the group policies and a documented location for where this information is kept. In an ideal world, printing off the settings would also be a good way to document the information too.