I have had that same problem off and on since the update. My only solution has been to restart the phone.
WiFi has also been a problem - every time the phone went to "sleep", wifi disconnected, and then wouldn't connect again when I tried to use it. I fixed this by keeping WiFi on during idle, but this just destroys the battery.
I have written to HTC about it, and they have escalated the issue, so I hope it will be fixed soon, because this is pretty major.
On another note, I just got an additional update a few minutes ago, about 20mb, just called "settings". It'll be interesting to find out what that is about.