Same problem - blank screen after attempting to load any app. I have now flashed CM10 and yet the same problem. I think the Tmobile modem is the issue. On reading around I realized one thing I never do that I should and will, that is backing up the modem/EFS before attempting anything. I hadn't done that with this phone. I thought I was getting the hang of custom roms but I did miss a couple of steps and I don't want to antagonize a situation. I am thinking these are my options now but I am not so sure,
1-Look for an ATT stock modem online and flash that or
2-Use Kies to restore? (I am hoping that that should restore the stock modem? I don't mind rooting it again from there)
3-Should I back up I have another i717 ATT stock ICS (rooted, stock ICS) that I can extract the modem from and flash that to the troublesome i717.
The details on that are here but I am not sure if this is the correct stock modem.
What is the best option? Again I am just trying to be careful before I mess this more than they are now.