How about that heading for SEO eh?
Anyway, this appears to be a problem with those people who have uninstalled R# from 2005, but also have 2008 installed. In this case it appears R# leaves intellisense off when it uninstalls. To turn it back on again select Tools | Options menu and you will see this form:
(If you can't see the form (Blogspot was playing silly buggars when I checked this earlier) its under Text Editor | C# | General )
Just put the ticks back into "Auto List Members" and "Parameter Info" and your intellisense will be back.