I have the exact same issue with my HVX200 (less than 2 years old). Had not used it in while and when I turned it on no buttons or menu items would function (goes straight in to record mode, could not even turn it off-had to pull the AC or battery to turn it off). I immediately called the Panasonic center (last Sat) and only got an answer this morning (Tuesday). I will be taking it into a service center today in my area. (L.A.)
My camera is in almost pristine condition, with very lettle use over the last 1-1/2 years (bought in Nov 2007), so I thought this was odd for the this to happen like this?
Reading this thread at least let me know I was not alone with this issue.
Ironically, I was just going to update the firmware for the new E-Series P2 card I just purchased, but never got that far.
Please let me know how your repairs went for you? Or any insights?
Thank in advance.
Alan Sheltra/AniMajik Productions
https://oncallfx.com