It seems to be working now. I tried adding my user to groups and deleting the user from groups with a restart of the workstation in between. It works everytime. I thought I had tried to restart before but apparently not. So it must be because of what Howerd mention about global groups only getting attached to the user's security token at logon.

Thanx for all your help and solutions. Sorry that I have created such a big thread when it could have been solved by a simple logoff/logon