For the list of buildings, check to see what tab you are using. There are 3 tabs: "newest", "old", and "all". If the game is stuck on old, you will not see any buildings unless you have researched the more advanced version.
I've tried to reproduce your problem. If you have the "old" tab selected, the game will remain stuck on "old" until you select a new tab. I found that things will remain stuck even if you start a new game, or load an old one.
You are going to need to change the tab manually to get things working. Otherwise, I suppose you could modify (or delete) your pref.ini file in "/My Documents/GC2TwilightArnor/" folder. Open the file in notepad, scroll down to the bottom, and change "ImprovementFilter=2.000000" from 2.00 (old tab) to 1.00 (newest tab) .