URGENT - Can't Get 1ShoppingCart integration working

I've got an _almost_ fully set up system going with aMember and VBulliten integrated ... works find if I do a manual add - or a signup.php add with a 100% discount coupon (bypassing 1ShoppingCart), but when I try it as a "real" user it doesn't go to 1SC.

It tries to load the 1SC page, this is the URL I see ...

Code:

http://www.marketerschoice.com/app/netcart.asp?MerchantID=dave186&ProductID=5828928&AMemberID=25&PostBackURL=http%3A%2F%2Fwww.morebuyerseverymonth.com%2Famember%2Fplugins%2Fpayment%2F1shoppingcart%2Fipn.php

... but the page never loads. It just hangs, and is blank.

Any ideas? I need to get this up and running ASAP ...

Dave

Yes - I've done both of these things and I'm still getting the blank page at my URL.

Just added it to support ticket BFQ-60243-585.

Thanks,

Dave

Any ideas? I contacted 1SC and they say things look correct on their end.