check out the other post, thers a loophole, click send as a gift, then email it to yourself!!! go go go
Actually I tried this, it still won't take payment. I've also tried to go through both Paypal and a differant card. I also called my credit card companies to make sure there was no problem with them being maxed out of anything (that would be a whole differant problem, since I shouldn't even be close), this is a complete mess on STEAM's part as opposed to on my end, and there is no real work around since the bottom line is STEAM isn't processing the payment.
If I had to make a guess, I'd say they probably borked activating it. The game is availible, but it didn't appear under "new releases" which seems to be a system glitch since that's probably automated. Our problem is probably that STEAM just really doesn't give a crud over a $10 piece of DLC and figures that they will fix it when they fix it, and have the game out tomorrow for their 1pm release show. Since it doesn't appear that Bethesda is willing to call them on it and make them actually do the job they have been accepting money for, we're pretty much stuck.
I'd imagine the guys who should be fixing this are all chowing down at Valve's super snack bar (I'm not kidding, "The Escapist" had videos of their facilities and did an article on their snack bar) instead of working, because it's not like we the customers matter since they already have us as captive audiences. We either have to buy it on their time or go without. The only ones in a position to do anything are the companies that hire Valve, and that pretty much amounts to them saying to either fix it, or they will pull out of the service and sue for lost income or whatever... but to date I don't think anyone has actually done that, given that we see things similar to this happening again, and again, and again, and everyone seems to be content to just let STEAM do it's own thing as opposed to operating as a professional entity.