I also had this issue recently with text messaging...Cause code 34 error code 2.
I did contact support but they were unable to determine the issue. It only happens in a certain area of my state, I can send and receive text messages just find where I live and work. But when I was traveling east, I had this issue and it wasn't until I was past the certain area where it worked fine again.
Support instructed me to contact them on my phone by dailing 611 while I am having this issue so they can trouble shoot. I will have to wait until I am in the area again but you may want to contact support and ask for a Tech Level2 for assistance.
I've had issues sending texts lately, but I get an error cause code of 97 class 2...
I read that on other HTC phones from way back when (Eris), the solution was to replace it. Don't know if that's still the case.