I'm using KH3 since 83 hours ago and the problem seems to be gone (nightly 116).
Additionally, some random reboots have been solved as well.
I'm in Spain, using Orange Network, and the original baseband firmware was KJ4.
The symptoms was; losing signal (3G), and in some cases (less often), random reboots.
EDIT: More than a week with this firmware (KH3), and the problem is gone.
Edited by kanutron, 23 February 2012 - 07:30 PM.