I have a weird problem. A colleague created an AD security group and added some existing security groups as members. I created a sharepoint group and added the security group. All seemed fine. I assigned the sharepoint group to a library and gave it contribute rights. All good so far. I checked a few employees using check permissions that i know are in the sub groups and am getting some weird results. Basically some users dont show as having the correct permissions whilst others do. Even stranger, employees that show the incorrect permissions can still edit the documents. So it seems the permissions are actually correct. Its just check permissions isnt.