Anyone having issues adding a custom amount for the humble THQ Bundle?

I can't enter a custom value. I don't have a lot of cash, but was going to throw in over the median for it (so $6.00 basically), but in the custom amount field it's grayed out and lists "$13.37." Is the site just overloaded? Or is custom amount no longer allowed?

Edit - Son of a bitch, it's a firefox bug. Well, heads up for anybody else who has issues, it's working in IE (shudder).