Can you not use System Restore to go back to when it was okay? Then add the critical updates one at a time to see if one causes the error.
I use WinMe and have installed all updates with no problems. I have read that some users have had a problem with the update KB891711. This is listed in Control Panel/Add/Remove Programs and is running at bootup. Cntrl/Alt/Del will show it in the Close Program box.
Extract from click here
"The damn thing messed up my computer. Was in startup items, and caused blue screen errors.
Couldn't get anything done on computer. I unchecked the KB891711 in msconfig, re-started and everything worked ok again."
You can uninstall it via Add/Remove Progs or stop it running from Start/Run/Msconfig/Startup. TC.