I just updated to 4.3.2 and now I'm am having codeSense sleeping on me at every turn. During coding I'm getting partial listings from enums, partial or no properties for classes, often no syntax highlighting, no errors for undeclared variables.
If I build the project it raises the right warning/errors and links everything right. So it actually can figure out if something is wrong, it just does not seem make an effort to do it while I'm writing code.
So angry right now.
I ran into a similar issue recently and I wound up Deleting the Derived Data for the project and the restarting Xcode.
In Xcode go into the Organizer and under the Projects tab select your project from the left and then press delete next to Derived Data. Then restart xcode and hopefully you'll be good to go.