Kicking me out of Payments on Websites

So today marked the third time I got kicked out when trying to pay for something. I was on Kickstarter, backing a project that still had 14 hours left to go. When I get to payment, a popup came up immediately telling me that my reward has been released. I tested it with other projects, and it only happens with limited quantity rewards, and only on Firefox. Earlier today, I was trying to reserve a room for a meeting tomorrow, and it kicked me out before I could finish. A week ago, I was trying to reserve tickets for a concert. I got in the queue and got in with seats to spare. I selected my seat and went to checkout. However, I wasn't able to go past the extras and add-ons page, the checkout button stayed grayed out. Lost the tickets. Is any of this related, or am I just having really bad luck?