I also have Bueno. And when I try to upload a header this message comes up: "Sorry, this file type is not permitted for security reasons." Its happened to others, as I've read online, but there is no clear solution.
I've tried logging out, logging back in. Still there.
I was experimenting with different headers just fine and then--I just can't anymore without that message coming up.
At best it will take me to crop the image, however, the image is not there. But a blank gray box, that isn't even where the picture would be had it actually uploaded. Instead its up against the upper left of the computer screen. Weird.
I can't even upload pictures I have previously uploaded experimenting with headers. Its just NOT working. I don't know what to do!
I hope mine just comes back for no reason like savvyjulie! (the commentor above) I need help in case that doesn't happen! Where would I begin to solve this problem!?