Good news Mark.
I am hopeful we have found a cure (possibly!!!) but a little annoyed that I don't know what was corrupted. I went through the "faulty" email contact data with the proverbial fine tooth comb and there was nothing wrong that I could see. So what little error was introduced? In my case I am pretty certain that it was done with "Easy Transfer" when moving from XP to Win 7 but in your case?
Oh well, I am sure there will be another little Microsoft problem to prioritise on and at least I don't have to go back and un-install Win 7 and start all over again.
Nice speaking to you and good luck.