When you do an online validation, you should see a phone number to use in case there is a problem. Try this before you reinstall.

 

XPS M1530, Vista Home Premium SP1, T7250 Core 2 Duo (2.0 GHz 800 MHz FSB), 4 GB DDR2 667 MHz RAM, 200 GB SATA II 7200 RPM, Nvidia 8600M GT 256 MB - 156.63 Driver, Wireless-AGN Mini-Card, BlueTooth, WSXGA+ High Def LCD (1680x1050) w/ 2 MP Camera

Dimension 9100, Dual-Boot Win XP SP2/ Vista Home Premium SP1, 3.0 GHz P4, 3 GB DDR2 533 MHz RAM, 160 GB SATA II Samsung (XP), 300 GB SATA II Seagate (Vista), 250 GB SimpleTech USB (WD Drive), Nvidia Go 6800 (425/825 MHz - XP, 400/800 MHz - Vista, Vista Driver - 169.25), Dell 1901 UltraSharp FP

Inspiron E1705, Win Vista Premium, T7200 Core 2 Duo (4MB, 2.0 GHz 667MHz), 2 GB DDR2 677 MHz RAM, 120 GB Samsung HD, Nvidia Go 7900 GS - 156.69 Driver, 17” Sharp UltraSharp TrueLife Wide-Screen WUXGA

It has been reported that one of the updates can cause this. Use Add-remove programs, select 'Show Updates' and uninstall the one(s) you installed before this happened. Wait a week or so before you reinstall it to give MS time to correct this.

Have you tryed to do a system restore so you can restore the computer before you did the update

Yes I have the system restored and running again fine, I have elected not to automatically install microsoft updates but not altogether happy about that. I first encountered this problem about 1 month ago and have restored the computer on 4 occasions since then after patching the updates.

I may try ringing the number as suggested in the above thread if I have no success.

Thanks