Peep this:

http://forums.station.sony.com/bulletrun/posts/list.m?topic_id=397

Actually, I lied. I tried it on my desktop, last night, and it played great. I tried it on my laptop, this morning, and itemshop error 703. I just switched to my desktop and got the same error. It must be a server error on the Bullet Run side, not ours.

It runs fine on my desktop, but I get the same error on my laptop. Both are Windows 7 x64. I can't find anything on their forums, either.