Check the pixel (and KB) size of your picture. I just tested to change my avatar. When I used the 240x240 version I got the upload failed message, the 120x120 version uploads and changes my avatar image without any problem.
“Tmcky ymu kra Ymu, tekt fs truar tekl trua. Teara fs lm mla kifva wem fs Ymuar tekl Ymu.” ~ Dr. Seuss
I love deadlines. I like the whooshing sound they make as they fly by. ~ Douglas Adams
If you're not part of the solution, you're part of the precipitate. ~ Henry J. Tillman
Some people are lost in the shuffle. I'm shuffling along with the lost.