Lightroom 2.3 crashes in Development module

Question

I am having a brand new problem with LR 2.2 & 2.3 with my Dell 730x 64bit 6GB Ram.  I am running VIsta Home Premium 64 bit.   I have been running LR 2 since it came out with no trouble - until a few days ago.
I also have a Sony Monitor as the #1 Monitor on the Nvidea GeForce 9800 GT using the Generic PnP Monitor driver from Microsft - 6.0.6001.1800 dated 6/21/2006.
I have a second monitor which I use for Lightroom: - Dell 2007FP Monitor with Nvidia GeForce 9800 GT Video card with all settings at defaults. The driver is NVIDIA v 7.15.11.7744 dated 7/17/2008. This was the original driver and has been performing well for months
This has worked splendidly since I bought this high end PC in Feb, 2009.
. In the last few days, however LR crashes any time I try to use the Develop module on the Dell monitor.  I get "Adobe Photoshop Lightshop 64 bit has stopped working" when I try to crop or use other tools at the top of the Develop list.  The lower tools like exposure changes the histrogram, but not the image. This also happens when I switch the driver on the Dell to the Generic PnP Monitor driver. This happens for NEF and JPG files.
When I run Lightroom on the smaller Sony screen, the photos don't display - only gray rectangles for photos. However, in the Develop menu, when I try to crop a gray rectangle, the image appears and the crop works OK. When I finish the crop, the image goes back to a gray rectangle. It does not, however crash the program. This makes Lightroom unusable since photos and thumbnails are not visible. I believe this may have been happening for a longer time, but since it worked fine on the larger Dell screen, I was OK.
All the rest of the LR modules seem to to work. .
Here's a list of things I've tried with no success - they all resulted in the Develop Module crashing LR.
The problem started a few days ago, so I went ahead installed the update to go from Service Pack 1 to Service Pack 2.  There was no diffrence.
I have re-booted with only MS services - no others and no startup using msconfig - same problem
I have deleted the preferences file and created a new one - no luck
I have imported new files - same sympton
I have loaded other catalogs - same sympton
I have uninstalled 2.3 re- installed ver 2.2 - no luck
I have uninstalled 2.3 and installed the 32 bit version of LR - same sympton
I have run chkdsk on my drive - no problems, no difference
I have removed the Develop Presets, External Editor Presets, Modules lrplugins, Local adjustment Presents from  AppData\Roaming|Adobe\Lightroom directory - no problem
I have tried to use system restore several times  - to dates prior to recent windows updates, but system restore won't work???
Photoshop CS4 64 and 32 bit work fine, but it doesn't have the speed of editing NEF files that LR does when it works.
Any other ideas on what to try? I have completely changed my workflow to do 80%+ Lightroom and loved it. The thought of returning to Photoshop is devestating!

Answer 1

FIXED!!
Thanks for the suggestions from those who replied. I spent 90 minutes last night with the Dell support team who provided me with a previously unaccessable new driver for my NVIdia GeForce 9800 CT - this one was version 7.15.11.8130 dated 12/30/2008. They also provided me with the new NVidia Display Control Panel.   This program is in windows/system32/  and runs with the file name: nvsvc.exe.
Two suggestions were to turn off this program. It was not running, and typically has not been running over the past few months. I started it to see if it made a difference. It did not.  Then I turned off and it still didn't change any LR problems. My guess is that there are some options that can mess stuff up, but I only had the defaults set.
Another suggestion from KDWAVES: Gray rectangles when using the Sony monitor is a sympton of a corrupt color profile. If you use color calibration, try re-calibrating the Dell. If you are using the default color profile, try changing it.
My Sony was using some default, so I loaded the Dell Monitor.icc color profile created by my color calibration hardware/software (Eye One Match v3) and appied to the Sony.  It worked and the gray images were displayed properly. Also all the Develop modules worked fine. I was a little disappointed, since the Sony is a smaller moniter and I bought the larger Dell Monitor specifically to be the color calibrated large monitor for photo editing.  So I moved lightroom to the Dell Monintor .....    AND IT WORKED GREAT!!   Thanks much KDWAVES!
I had only calibrated the one monitor since both monitors were run by the NVidia video card and it seemed to only run one color profile at a time. I didn't bother to calibrate the Sony, but just adjusted the color controls manually to make the screen look like the Dell.  Now that both monitors have the same color calibration file, everything seems fine.
I've listed all the details for the next person who gets this surprise. I still can't figure why it ran OK for the last few months, on the Dell monitor.
I can't thank you guys enough for helping. Maybe the next victim won't take the five days it took me to unravel this one.
This is my first Vista machine and I bought theVista 64bit version and the Intel Core i7:  quad & hyperthread processers for the Adobe 64bit software. When I'm not chasing bugs like this one, the machine and the Adobe software run REALLY FAST. I have been able to double my photo coverage since the Lightroom RAW file import / export / render / edit and everything goes about as fast I can click the keyboard - unlike any of the Adobe stuff has behaved on my prior PC's. I have even switched my sports photos to LR exclusively since it's so fast,
P.S. CR Henderson's advice on a new Nvidia driver dated May 6th 2009 is great idea. I will be hunting for that next.  I have not had any Photoshop CS4 problems in either 32bit or 64bit versions (except not many plugins run in the 64 bit version). But I didn't buy this PC until I confirmed that my NVidia GeForce 9800 CT video card was on Adobe's approved list.