Well, that's just fucking great.
I was buying several stocking stuffer/gifts for friends on my Steam list, and everything was going fine. When I got to around the 9th purchase I received this message - There has been an internal error initializing your transaction. Please contact support for assistance. I get it for my credit card, and for Paypal. I can't even add funds to my wallet now. I know I have plenty of money in my accounts, so this has to be some sort of automatic denial that kicks in after multiple purchases in a row. I contacted my bank and they said there was no auto block on their end, so it's all Valve.
There was one thing I wanted for myself that ends today, and I'm probably going to miss out on that now. If I end up missing out on the rest of the sale over this, and can't do the rest of my gifts, then Valve can pretty much kiss my ass forever.