If you suspect GPO and can't figure it out, try this: document your GPO settings (use Group Policy Management console and you can get a screen shot of the settings). Then, once you have documented the settings of all of the GPOs your problem user has applied to it, create a test user and a test OU, apply a test GPO and apply your settings one by one until you find the setting. At this point you have identified your issue so all that remains is the ugly, time consuming process of figuring out exactly what setting is hosing you.
