After installing ReSharper 3.0.2, I decided to disable the Addin while I was using C# 3.0. However upon disabling it in the Addin manager, I no longer had intellisense.
To re-enable it, go into the Options > Text Editor > C# and tick Auto List Members. You will then be able to develop again.
This is the same for both 2005 and 2008