I'm using After Effects CS5 running on Windows 7, and I've never had any real issues like this before.
Essentially all the properties here:
have vanished. I do not know how to get them back, and I've never seen anyone experience anything similar like this before.
Can't put it plainer then that. I haven't installed any new updates or similar since last I used it.
You have probably hit the layer or transfer buttons in the bottom left corner of the timeline window. Press that and your modes should come back. Or just right click on the columns line(source name, parent...) and just choose "switches" or "modes"