I had a very odd situation and I dont know if it is because of ice on wings, but in CRZ level suddently the aircraft start to bank very hard to left and right, then I switch off LNAV and try HDG, it doesnt help, the bank angle was above 45° and I command AP off, and flying manually was impossible to control the aircraft, looks like a broken joystick, but it wasnt! my joy is ok and I calibrate before every flight.It is not a AP malfuction since manually was very hard to control the Aircraft too, its sounds like a flight controls issue, hidraulics or ice on wings? but in FL370 there is no ice...I guess.In flight I command systems maintenance (because I fly with failures ON, in SP2 I sugest to allow that only on the ground) and helps a little, than I turn ON wings anti-ice and I recoverd the control of the airplane after a short time.So, the ice on wings is modeled in the 737NGX? Anyone had an issue like that before?

Sounds like a weather issue. Try disabling turbulence.

The problem that causes this is turbulence. Read more about it here: http://forum.avsim.net/topic/350389-my-weather-config-for-pmdg-planes-part-ii/page__p__2127745__hl__weather%20settings__fromsearch__1#entry2127745

Thanks guys I will give a try!