I've recently upgraded to 2.3.7 and noticed a new setting under the Google accounts sync options. Settings->Accounts & sync->my google account As well as sync contacts, GMail etc it now ...
I have two GMail accounts active on my Android 2.2. Let's call them Acc1 and Acc2. Acc1 is the default account I set when I got my Android. I didn't know then, that I can't change the default ...