We just came across this issue with the RC1 release of IE8 and thought we should pass it on…
Unfortunately, it looks like You will not be able to view Windows Internet Explorer Group Policies on Windows Server 2003 or Windows XP 64-bit Edition with Windows Internet Explorer 8 Release Candidate 1. If you open the Group Policy Editor (gpedit.msc) after the initial installation of IE8 RC1, you will see a warning dialog stating that the inetres.adm file could not be loaded.
NOTE: You will still be able to view and configure Group Policies unrelated to Internet Explorer.
The problem occurs because the Group Policy Editor on Windows Server 2003 and Windows XP 64-bit Edition cannot parse a particular line in the inetres.adm file.
To resolve this problem for IE8 RC1, do the following:
1. Download the updated inetres.adm file in the language you want from here.
2. Copy updated inetres.adm into %WINDIR%\inf\.
3. Click Start, click Run, type gpedit.msc, and then click OK.
With these steps you should be able to view Internet Explorer Group Policies without receiving any errors within the Group Policy Editor.
NOTE: You should not see this issue with the release version of IE8.
Here are direct links to the IE8 RC1 .ADM file, as well as a spreadsheet which lists all of the policy settings currently available:
The IE Support Team