I am sorry to hear that you are having problems, stick with it though because the pronto is worth it!
I do have a few suggestions, but I am sure someone else will come up with better ones. I would suggest hitting the reset button on the back of the unit, I think you need to do that during an update of the OS (it has been a while) anyway, but it can't hurt.
I would also suggest touching the screen before you start the update to "wake it up". I don't know if that helps or not, but it is part of my voodoo like ritual for loading ccf files to the pronto.
I would also suggest waiting 30 seconds or so before trying the update again after a fail.
Here are a couple of threads that may help you out:
[Link: remotecentral.com][Link: remotecentral.com]Good luck! Hope you get your pronto up and running soon.