Same problem, HTC Desire S on Orange with Android 2.3.3 HTC Sense 2.1, software 1.47.61.1
I have the update to 2.3.5 available - in fact, it's been available a while, in fact, I already applied it once and it pretty much totally bricked the handset ( constant crash-reboot cycles ).
So, I got a new handset from Orange and left it well alone.
But I still have the signal dropping issue.
So, the question is, has anyone had any issue with the 2.3.5 update? Should I crack on and not worry about a reoccurrence of the 2.3.5 issue?