The data timeout seems to be the cause of the phone answer problem.
http://forum.ppcgeeks.com/showthread.php?t=40427
I was having the same problem on the sense 2016 rom and almost every rom I have used. I did the regedit in the above thread this morning and have had no problems answering the phone all day.
You lose the ability to have your data turn off after timeout but I use the comm manager and manually turn it off. I figured it wasn't much of an issue to me personally.