Laptops freezing after login

We've had a problem on our network over the last few weeks and I can't fathom what's causing it. A member of staff will log in to their laptop, the desktop will appear but the machine then freezes and has to be powered off to get going again. Sometimes the second time it'll be fine, others it'll take three or four attempts.

This seems to happen to some staff more than others (either that or they're the only ones that bother to tell me there's a problem...) - some with laptops only a few months old, if it was just those with older machines I could understand it. All laptops are running XP SP3 with Office 2010, servers run Server 2003 R2 standard. One server holds the staff emails and shared documents, the other holds profiles for staff and students.

Problems seem to be getting worse since we had some network upgrades - gigabit switches installed at various points in the school. I can't see why this would cause the issue to get worse, but it's the only thing that's changed recently. Nothing showing up in the server or laptop logs as far as I can tell, does anyone know what the problem may be?

Sorry that this is a bit vague, but school broke up on Friday and the last few weeks of term are so busy I haven't had much time to look at the problem.

Not much info, but let's see where it goes.

With there being nothing in eventvwr I can't see this being a problem specific to your workstation or server hardware otherwise something would show up in system or applogs. Have you changed any GPO settings recently that are not getting applied correctly to some laptops? This could be down to AD replication if you have done. Just type replmon in the run bar and add your servers and check that replication is occurring correctly.

Next thing to check is network loops. Do you have any other problems on your network - voip phones working intermittently, printers acting in a bizarre manner. If you have HP switches, just connect your laptop up to one of the switches an affected device is on via a console cable and if it has loop protect enabled, type show loop-protect all on the command line. This will show you if you have any ports with a loop and how long it has been up. We have had issues where a student (or staff member) has looped 2 sockets next to each other and we have had an older switch without loop protect at the top of a stack which has brought entire areas down.

Next thing - you say you had a recent network upgrade. Who did this? Did they configure anything they didn't really know what it did such as spanning tree? This can really mess a network up if you don't get your costings right. In an education environment, I can't see why you would really want it anyway.

Any other information would be helpful - did it start only after the network upgrade, did you make any other hardware/software changes recently.

Pete - see the other thread I posted, with the same title, at the same time for some reason. Seems to be a GPO problem which I now hope is sorted. Thanks.