Thanks for the reply..
Yes, I'm using a different paypal account to pay other than the paypal pro one (paypal will stop you if you try to use the pro account associated with the store anyway!)
I'm also currently using three different browsers..
Safari / Chrome / Firefox (All latest versions)
And I've quit them all, restarted them all, and then retried with them all.. and still I get the same failure results!.. :-(