boot camp: control panel crashes, kb & mouse not working, can't boot into OS X

I've just installed Windows 7 Professional 32 bit on my iMac 20" mid 2007 model, I used bootcamp to prepare a partition, and formatted it (all according to the manual). After booting Windows worked, and my Bluetooth Apple Keyboard and Trackpad worked, although I had no special Trackpad support (e.g. couldn't scroll or right click).

So I installed http://support.apple.com/kb/DL1630 -- Bootcamp 4.0.4033 -- this was already put on an USB flash drive by the installer. It installed a bunch of things, and then the problems started. After rebooting:

• Keyboard doesn''t work at all.
• Trackpad doesn't work at all.
• The Boot Camp Control Panel crashes immediately with an error in ntdll.dll. If I click on the Boot Camp diamond and select 'Boot into OS X' it says it can't find my OS X startup disk. (I can still access it by holding down 'alt' while booting though, so nothing is really broken there).

Trying to add the drivers manually or discover the mouse/keyboard doesn't yield anything. Windows sometimes sees the trackpad as a bluetooth device but refuses to pair.

I tried repairing the install and uninstalling, redownloading and reinstalling it (and also repairing the re-install) but the problems remain, so I'm pretty stumped. I searched these forums, but there don't seem to be that many people with a crashing control panel.

Windows 7 is fully upgraded as well.