I'm having an even weirder problem.
I bought my phone through Amazon Wireless and they sent me instructions to install the Appstore and some free apps.
I downloaded and installed the Appstore. After I signed into my account it opened up fine but I was on the UK site -- everything was in pounds and my free apps were not showing up per the email.
I do have an account on the UK site as well, so I figured I must have mixed up my account settings. But since I coudn't figure out how to change them, I uninstalled and reinstalled the appstore.
This time, when it opened, it said that I had changed my country. But when I said OK, it gave me the error that others were getting and closed down.
So I went to settings and cleared the cache and the data, thinking that maybe it would start over and allow me to reenter everything. But when I went back, it gave me the changed country message and then opened up to the UK account.