We have been experiencing similar issues for a while.. We have currently installed 10.1 on a Test Server but plan to roll it into production to replace our existing 10.0 ArcGIS Server by the month of May. But I guess we aren't making the deadlines because of the performance issues..
Local browsing to 10.1 Services whether with ArcCatalog or with IE is pretty fast on the Server itself, however as soon as you go to a client machine and pass the intranet + the Company Active Directory Groups, the performance is agonizingly slow.. And this is only while browsing through the ArcGIS Server Folder/Directories, direct URL's to any of our map services work just fine within out client applications..
We have been working with ESRI Tech Support for the last two weeks, but nothing productive has come up yet. Any suggestions here?
Regards,
Muneer Majid
Spatial & GIS Analyst
Chevron Energy Technology Company