[HTC One V] Umpal:
How did end your case? I'm asking because I'm experiencing exact same problem - however on stock not rooted system:

Android version: 4.0.3
HTC Sense: 4.0
Software number: 2.22.401.6
HTC SDK API level: 4.11
Extension version: 403_1_GA_5
Kernel version: 3.0.16-g133e482 root@abm024#1 PREEMPT
Baseband version: 20.79.30.0835U_3831.24.00.23_M
Build number: 2.22.401.6. CL92876 release-keys

My phone went to the repair service under warranty because of the annoying not working well power button and yellow spots on the screen. When I got it back the power button worked flawlessly only for some month and a half and now it's the same problem as before (LOL) but the LCD screen has been replaced and is wonderfully constant white in every place of it and even the surface is smoother than before! (it has definitely better material of Gorilla Glass, believe or not.) However I noticed carrier signal problems. Before that reparation it never gave me a problem. In comparison to other phones mine always had better visible signal (more bars.) Unfortunately it has changed. I don't remember on what version of baseband it has been running before but as soon as I got my phone back I received an information from network about new update, which I commit practically instantly. Since then the problem is as described. It is hard to tell what is the cause because it could be fault of the "technician" who had it in his hands, it could be his update (to some different version than I sent them), or eventually the update I made.

I'd like to experiment with different basebands but I don't know where to get them (I mean official ones) and if it's even possible to do it on my not rooted phone (I want it to stay like that since it's on warranty and I don't want to loose it yet.) Any suggestion?

One more thing: I never had to care how do I keep the phone in my hand - it always worked excellent, no bar(s) drop.

Oh, and it happens on different SIM carriers that use different antenna, so it's definitely not the carrier/company problem.

[Update]

SOLVED!

I ran a test with two different SIM cards and here is what I've found:

One of the SIMs is the Internet only card and works in Orange carrier of Dominican Republic (it doesn't matter much but I'm telling it just for your knowledge.) That SIM does NOT work in WCDMA network mode on HTC One V. Only 'GSM only' network mode works. As a consequence EDGE speed is maximum I get (what's curious on Xperia Ray I get HSDPA but that phone does not say if its network mode is GSM or WCDMA.) Next I put another SIM card (Claro Dominicana), which I use daily for calls. This one works on 'automatic', 'GSM only' or WCDMA. I noticed that my loosing signal problems was due to automatic. When I change it to 'GSM only' or 'WCDMA only' it keeps strength signal all the time. However on WCDMA network mode the battery was drained rapidly (~30% in short time but can't recall how long it was, maybe couple of hours at most.) Then I changed it to 'GSM only' and left the phone for night long. In the morning I noticed only 3% drop. I am satisfied :)

I hope the experience I'm sharing with you, dear fellas, will help someone who faces similar problem.

Cheers

[Update 2]

Another night and this time only 2% battery drain. I didn't notice any signal lost or even strange behavior.