Error message while trying to change header

I am trying to change the default header image to one of my own, but I’m getting an error message:

An AJAX HTTP request terminated abnormally.
Debugging information follows…

I can’t copy and paste from the text box, but will add the additional information, if needed. Is this something on my end that I can correct? Already cleared my cache and rebooted both my computer and my browser.

Any help is appreciated!

@zen.harmony As long as the image is 980x240 pixels it should work. Do you know the size of the image you are uploading?