I have been having problems with PVMtpServicestart basically since the first day a got my Thunderbolt. The best I can find is that this process is related to Digital Rights Management and is constantly updating leading to the battery drain.
So far I have found that the Blockbuster app, USB Media syncing and restarting the phone all start this process. If I go in and force stop the process as soon as I restart my phone it seems to be fine, but if I sync the phone via USB even force stopping the process doesn't seem to work. I have not seen anything to indicate that HTC is aware of or looking in to the problem.
Another thing to try
I don't know if this will help and I apologize for being a little vague - I was so annoyed by pvmtpservicestart using 70% cpu that I was trying different things a little randomly.
Tried the Blockbuster tricks with no success. I realized that I had done a music sync using Windows Media Player and started looking into DRM things. I used a file manager to look at contents of the SD card and deleted the folder called Music and one called Albums - both put there by WMP.
Then I noticed a file called something like "com.htc.blockbuster" - probably not the correct name but something close to that. Just for fun, I deleted that (bit of a gamble since it could have messed up the phone). Shut off and restarted the phone and pvmtpservicestart was gone.
I then reloaded the Music folder using drag and drop from my PC rather than sync, installed Amazon Mp3 player and everything has been working well since.
Sorry for the vagueness - I really didn't expect to clear up the problem or I would have taken notes.
The same thing was happening to me. I tried everything suggested to no avail (blockbuster, background services, etc.). I did notice a couple commonalities - 1. people who have this issue (myself included) seem to have been messing around w/plugging their Thunderbolt into the USB ports on their computers (either trying to sync or use as Internet passthrough) prior to noticing the PVMtpServiceStart service, and 2. the few that did solve the issue ended up having to reboot. I downloaded and installed "Advanced Task Killer" to see if I could kill the process that way. It worked, however, the process would restart after a few seconds. I then tried running the Advanced Task Killer again and then immediately rebooting my thunderbolt (my theory, don't give the task enough time to restart) and it hasn't started back up since!
Since I don't use Blockbuster, I just hit the "clear data" button in the application menu. Then, I did the same for the app in question. I have connected my laptop to Verizon's 4G service through the USB internet pass through. I haven't tried to add any music by syncing with WM. I have also used the TB as a disk drive for my computer with no problems. Right now, the PVMtpServiceStart shows up as running, but has 0 KB of data size, does show up as running in the running services menu, but doesn't appear in the battery usage screen.