Windows update seems to have broken my X220's FN key

[jhh]

Last week I installed the recommended Win7-64 updates, and since then my X220's function key (thinkvantage as well) has stopped working under Windows. It's not a hardware fault as everything works fine under Linux, the thinklight (not dependent on the OS) can be turned on/off under Windows, etc.

I've reinstalled the drivers, all the registry entries appear to be normal, etc. No new software has been installed under Windows, so I don't think an app is intercepting key presses. The Ricoh SD card reader's driver appears to have broken as well.

Short of reinstalling, does anyone have suggestions for what to look for next? I'm a Linux guy, not a Windows one, so I'm somewhat lost.