I think the .jpeg extension is an Apple thing originally (maybe), and maybe that somehow didn't get along with your non-Apple computer/operating system. I seem to recall, in the past, needing to change the .jpeg extension to .jpg in order to view the photo. That was probably been back in the Windows 98 era.
There are far greater computer wizards than me around here. Maybe they know something.
When you say it said "jpeg", are you just saying that the image file had a jpeg extention, or was this part of an error message. If it was part of an error message, what was the full text, and did it occur before or after you clicked on "Upload Avatar".