File associations (always open with) are constantly reverted

Hi, This sounds like a minor problem but is a major hassle on every workstation. We want to change file associations for all types like opening all .eps with illustrator instead of Preview.app and many others. Our Workstations run Lion 10.7.1 and have Network Homes hosted on a Snow Leopard Server. Whenever the user changes the file associations (Get Info... dialogue) this change is reverted after a reboot. Strangely enough the new association is still in place if the user just logs out and back in again. There is no such problem with local users on the machines. The com.apple.LaunchServices.plist where these settings are stored reflect changes made in the Get-Info dialogue. Upon reboot the Finder seems to ignore this settings file although it stays unchanged! Any help is greatly appreciated!