D90D7 WES7 screen lag when dragging explorer windows

using WES7, with more than 1 explorer window on screen if we drag a window anywhere around the  screen we get lag and ghosting  - the screen quickly refreshes to remove it but it is noticeable and appears to be following through to the citrix VDi's too.  Our original build did not do this but we have installed so many windows updates, flash updates, HA agent updates etc over the last 2 years could one or more of these be to blame ?  are we better off just getting the latest WES7 build for the device and starting afresh ?

thanks