When uploading new images via the "Add New" in "Media", the progress bars freezes at a random spot (in the multi-uploader), and the percentage complete stops (in browser uploader). Neither allows me to add any new images to the media library.
If I leave it for a few minutes, the progress bar sometimes fills completely as if it had finished and says "crunching". But this never finishes. I've tried leaving it for long periods of time. No luck.
I've done all the PITA stuff. Cleared my cache, disabled all plug-ins, changed theme to twenty twelve, etc. Have also tried re-installing 3.5. (I get no errors or messages.)
The only thing I have not tried is to re-install 3.5 manually. As I think this may be above my skill level.