I had done a system reinstall, and was updating various programs, and at some point, I restarted the PC, and was promptly greeted by a blue screen of death (complaining about vidstub.sys).
But safe mode works ok.
I quickly found out that the problem was caused by my recently updated version of bootskin (V1.05). Until recently, I had been using V1.00, and it never gave any problems.
Oh well, I delete c:windowssystem32driversvidstub.sys, and restart. I then uninstall bootskin 1.05 and install V1.00, and then everything works just fine.