Downloading the latest upgrades for Mac 10.8.2 keeps stalling. I still have Firefox 17.0.1. the system has tried many times but the process just hangs.
Try to create a new profile as a test to check if your current profile is causing the problems.
See "Creating a profile":
If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.