We have recently upgraded our network to Windows 7 clients with Windows server 2008 servers. The upgrade was completed by the end of September and until now has been fine (apart from the minor bugs).

Recently (within the last 2 weeks) we've notice all computers on the network (around 1000) start to slow down to the point their unusable. It starts at about 08:45 and finishes at 09:15. Because of this, we think something may be broadcasting across the network.

This happens every day, between these times. I cant use my computer at all at the slowdown peak, and looking at task managers performance graphs, Physical memory is hovering around 35% and CPU usage is at 0-10% (idle) yet still crashing.

I've looked on DHCPs server log and cant see anything which stands out.

The only change we made prior to the slowdown was installing adobe CS6 on some computers, however the slowdown affects computers without CS6.

We have 2 physical machines, each with around 5-7 virtual machines running on them with ample memory.

Does anyone have any suggestions as to what we can do to narrow down whats causing the crashes? Any help, suggestions or advice would be appreciated.