There are two camps of folks out there: the press-and-hold-Trimmer and the tap-Trimmer camps. Each approach works,
but pressing and holding the Trimmer button during an attitude change (e.g., bank to the left) is a good practice to get into if you plan on using the autopilot and maintaining smooth transitions (more about that in an upcoming article!).
The fact that your controls "lock" with patch 1.0.1 is probably unrelated to the autopilot, however. After the pilot releases the Trimmer button, the new Trimmer logic implemented in 1.0.1 waits for BOTH the cyclic AND rudder inputs to be centered before the helicopter will respond to those inputs. For example, if a pilot releases the Trimmer button, centers the cyclic, but leaves the rudder a bit off center, the sim ignores BOTH until BOTH controls are centered, the helicopter is a smoking crater, or the cows come home*. This Trimmer lock is why many pilots have opted to revert back to the "old" Trimmer (which you can select in the options menu). Big kudos to the ED folks for leaving that option up to the user!
If you don't think this is what caused your issue, and you can repeat it, save the .trk file and post it up at the ED forums at
www.digitalcombatsimulator.com. They got some pretty smart guys over there who can diagnose it for you.
[*I haven't fully tested this condition yet.]