It might be. I think the R800at is the same as the R800a, and I run an R800a (was Telstra Australia branded, their 3G bands are different). All I can suggest is to move the Phone.apk from the hotfix into the original v0.2 ZIP and start from scratch.... but maybe it is an R800at issue in which case I'll need a logcat. EDIT: If you can't even get to logcat then it's a kernel issue.
Fixing compass (orientation) is really annoying me, it seems to work fine in MIUI Compass and GPS Status but does all retarded crap in Google Maps.
I put the Phone.apk in the main zip and flashed but it didn't make a difference. It won't get far enough for me to get a logcat, its hanging before it even gets to the rom boot animation. I can flash any other rom and it doesn't have a problem. I think I had the same problem when I tried flashing the other ics MIUI rom from the forum.