Background error message when uploading

Hi,

I have the latest version of wordpress with the Prophoto2 (2.1) theme.

I keep getting this error message when trying to upload a background image:

String (11) “background.png” Something went wrong.

The image is a small 20 kb .png file. I have also tried it as a .jpg, and a .gif to see if that makes a difference, but I still received the same error message.

I had a background uploaded for about a year, then I decided to change it recently, and experienced this error message.

Any idea what might fix this?

Thank you for any help at all!!!

elaine