I just purchased and set up domain mapping for my wordpress blog (dondueck.wordpress.com) so that I can see it under a domain I already own (dondueck.com). I had previously set up my dondueck.com domain (purchased through NetFirms) to redirect traffic to dondueck.wordpress.com, but I decided I'd rather have my wordpress blog's address appear as dondueck.com instead of dondueck.wordpress.com.
After updating the nameservers on NetFirms and waiting until WordPress saw the change, I added the dondueck.com domain to my WordPress blog. When I set dondueck.com as my primary domain and try to browse to either dondueck.com or dondueck.wordpress.com, however, my browser goes into an infinite loop between the two addresses (with nothing being loaded). If I set dondueck.wordpress.com to be my primary domain, then everything works fine (except for the fact that my dondueck.com redirects to dondueck.wordpress.com instead of vice versa, which is what I want).
While the infinite loop is going on, the address bar shows:
and this is the page source that appears is:
<HTML> <HEAD><META HTTP-EQUIV=Refresh CONTENT="0; url=http://dondueck.wordpress.com/"> </HEAD> </HTML>
Blog url: http://dondueck.wordpress.com/