first post as I found this thread via Google.
I have a desire s that's exhibiting the signal drop issue after the firmware upgrade to 18.104.22.168
That said my DS works fine in areas with strong signal but in weaker areas it'll drop out and not return.
I'm on T-mobile/Orange
I have noticed that with the DS aerial being in the battery cover, taking it off (so breaking the aerial connection) and replacing it sometimes solves the problem.