Intellisense really does have a mind of its own. I installed SQL 2008 R2 on my dev machine side by side with my existing 2005 installation and Intellisense worked fine. Granted it has some really annoying habits. (Dude, I typed a valid keyword followed by a space – why did you change it to something completely different?) But on the whole I like it. Then, about 3 weeks ago, I wiped the machine and did a clean R2 instal. Could I get Intellisense to work? Could I f***! I scoured the web and followed a whole load of magic voodoo rituals but nothing worked. I was resigned to trying a repair and/or a re-instal when I had nothing urgent to do. (Ha!) But this morning, out of the blue, it just started working. I guess one of the Windows updates mended something. Who knows?
So if your Intellisense doesn’t work, just keep calm and carry on. It will come back one day all by itself. Probably.