I experienced something like this too, but not with apps to SD, just with a nearly full SD card. I knew thats what it was because of the behavior the phone went through when it started up.
First it would boot, of course.
The UI would come up, it would start to run boot operations.
At this point the screen would work just fine.
Once it mounted the SD card, and started to hustle through the files, it would hang.
So to be sure, I restarted the phone.
This time when it booted, and I could get into the menus I opened up settings.
I went to SD card/phone storage, and touched unmount SD card.
This stopped the process of mounting the external memory, and my phone worked just fine.
Of course, being as thurough as I could be, I went back in after a few minutes, and remounted the card.
Sure enough, the system hung, and I had to restart.
If you think this could be the problem with your phone, give these steps a try. If they work, as in, your phone only hangs after it tries to mount the SD card, then you need to clean out your closet