Optiplex 390 video resolution problem

I have a recently acquired Optiplex 390 with a core i3 and Intel's HD 2500 integrated graphics running W7 Pro 32 bit. It is hooked to a 22" ViewSonic monitor thru a Trendnet KVM switch so I can share it with another computer.  All seemed fine for a few days then I noticed the 390's resolution got locked into a 1366 x 768 resolution and was showing up as a "Generic non-PnP monitor" instead of its actual name. I rolled back a driver update and all seemed well and it happened again. Soon I realized it would show up as a ViewSonic monitor at it's native 1650 x 1050 resolution if I started that computer first and was only identified as a generic monitor locked into a lower resolution if I started the other computer first then hit the switch on the KVM to change to this computer so I always started the Dell 390 first. Now the Dell 390 only identifies my monitor as a generic non PnP and is locked into a 1366 x 768 resolution regardless of whether I start it first or even bypass the KVM switch and plug the monitor directly into the Dell 390. Adding insult to injury is the other older Dell computer always identifying the ViewSonic  and going directly to its native resolution. The Dell 390  is locked in at 1366 x 768 and gives no other choice. On the plus side it is easier for these old eyes to see things!  

I've tried rolling back the driver, updating the driver, and system restore,  My story starts just after reinstalling the OS and I waited a few weeks to be sure all was well before adding my well used Microsoft Office 2007 product key and would hate to have to start all over.  Does anyone have any ideas aside from wiping everything out and starting all over?