No, no changes that we're aware of and you're the first to report such an issue. We'll do some investigation, but in the mean time, check:
* The /tmp directory is writeable
* Try looking in the /tmp directory for one of the images that is causing issues. See if it exists, is 0 bytes, or if it's a real image. All of those will help narrow down where the issue is.
* Let us know what extension you're importing the avatar into
Thanks,
Alex