I am stock for now, and tried removing Chomp, but had the same results.
I was wondering about the connection strength as well, but ruled that out when I would restart in the same location, have someone send me a test text and it would come through fine. I am not sure what causes it to stop working, but once it stops it won't work anywhere until I restart.
In my google searches I found that the Incredible was having the same problem after upgrading to GB. I also recently upgraded, so maybe there is a correlation. HTC issued a hotfix apk for the Incredible problem and, out of desperation, I actually applied to that fix to my TB (dangerous, I know).
I had also just did a battery pull, which I had not tried before, and things seem to be OK for now (as it would after any restart), so I will see how it goes. Unfortunately, if the problem is solved I will never know whether it was the battery pull or the hotfix, for future reference!