'll share my experience in some detail:
There are 4 steps. Download-Verify-Upgrade-Finish
It locked on step 3. 0% progress. I waited 10 minutes.
I took the battery out of the phone.
PC Studio recognized something was wrong and gave me instructions on how to recover from "critical failures" (or something like that). It told me to
i) disconnect the USB cabe
ii) boot up the phone in recovery mode (giving instructions on how to do that - volume down, camera + power buttons)
It said I would get a 'recovery message' and that one recovery is complete I should continue.
(At this point, NPS studio was presenting "next" and "finish" as options - I left NPS alone and focused on the phone)
However, my phone didn't do into recovery mode when I followed the 3 button power on sequence, it went into a black screen with a bright blue sim icon, and a "downloading" message. Having seen some flashing tutorials on the web, I recognised this screen as a good thing.
So I plugged the USB cable back in and click "next" on the NPS window.
NPS then tried again from the start :
- Step 1 was already done (downloading the firmware), so it skipped that.
- Step 2 it did again (checking validity of download)
- Step 3 then progressed quickly (only a minute or so) for the actual upgrade.
- Step 4, It finished.
The the phone re-booted which took a while. It stayed on the Samsung logo for quite some time (over a minute) then came to a basic home screen with the "initializing" message.
Then, all was well.
I notice someone else just killed NPS in task manager and tried again. Seems a bit easier than my method.
Although lots of people are having trouble, I get the impression that if you try again, it'll work.
Good luck.