[andi]

Guys, when I switched to JPEGs (shooting RAW only so far),
my camera started acting weird, I couldn't display the pictures taken and it was
locking to the point of not displaying anything at all - no menu, nothing.
Had to switch the camera off and on to have the display work, but
the problem was coming back every few images taken.
Now I'm back with RAWs, it seems to work, but it's taking much longer
for an image to be displayed after the capture... Have tried a few SD cards,
all the same.
I guess I should send it to Arizona...

[snofox]

My cameras act weird like that when the battery is low. Put in a recharged battery and see if it happens again.

[JeffJS]

Go through and do all the resets in the menus. It's a pain in the butt but when I've come against something that didn't go right (for some unknown reason), the resets cleared it up.

[JohnBee]

Guys, when I switched to JPEGs (shooting RAW only so far),
my camera started acting weird, I couldn't display the pictures taken and it was
locking to the point of not displaying anything at all - no menu, nothing.
Had to switch the camera off and on to have the display work, but
the problem was coming back every few images taken.
Now I'm back with RAWs, it seems to work, but it's taking much longer
for an image to be displayed after the capture... Have tried a few SD cards,
all the same.
I guess I should send it to Arizona...

Try leaving the battery out overnight while fully charging the battery.
Then reset all setting and try again.

Also did you try with difference lenses?
Apparently a lens can cause some very strange problems.
I know this may sound rediculous but someone else here chatting with Pentax support once fixed some strange problems by cleaning the contacts and/or lens mount(don't remember what they were). But it couldn't hurt to try right?

[northcoastgreg]

I couldn't display the pictures taken and it was locking to the point of not displaying anything at all - no menu, nothing

I've had a similar issue, except that it occurs while shooting Raw (I've never shot JPEG) and it seemed to get worse when I upgraded the firmware. I can get around it by taking another picture or going into liveview; and it's not a problem if I shoot with the self-timer. I suspect it might be related to the type of SD card (my upgrade coincided with the use of a SanDisk Class 10 32MB card), but I haven't tested it enough to be sure.