Help! Submit Order button on website is disabled for some customers

We just launched our new NetSuite-based website last night.  We’ve only had one real order come through the website.  (We usually get about 8-10 orders a day, so very low volume.) We’ve had two customers call-in and say that they got logged in, got all the way through the checkout process, then on the final screen the Submit Order button was grayed out and they couldn’t submit their order.
I’ve tried many, many test orders.  For the most part, they’ve gone through fine.  I did have one night, 6/28/10, when I kept placing test orders over and over that I did encounter the grayed out/disabled Submit Order button a few  times.  I had it happen in IE 8 and FireFox.  After awhile it stopped happening and I could never make it happen again, so I decided maybe it was because the same test customer was sending so many orders through the system.   However, now that two real customers have called in on our first day of having a NetSuite