Sorry you're experiencing difficulties with the image upload. My guess is you're using Internet Explorer version 6. One workaround is to use IE7 or Firefox. As Megan pointed out, just go to the Edit My Profile page and click on "upload a picture". You should get a popup window with a space to upload a picture or pick one of our own pictures.
We are releasing a much improved upload process some time next week that should resolve all these issues. Thanks for your patience.