batt. charged, pwrs on in playback mode only, powers down when I change mode, shutter not openning,

tried camera reset, hold down menu button for 5 sec. didn't help. Holding "DISP" button no change either.

Well, a few possibilities, the battery could be faulty, or has lost capacity to the point where it can't effectively power the camera in capture mode. Lithium Ion batteries do lose capacity over time (about 8% a year, compounded) and as such, even when showing a full charge, won't have capacity to power the camera. So you could try another battery. If the problem persists, then you have eliminated a depleted or faulty battery as the problem. Also, clean the battery contacts witha a pencil eraser. The contacts can get grimed from skin oil, dust, dirt, etc. Cleaning them off can restore a complete connection between the camera and the battery.

Try resetting the camera and installing any new firmware updates. Lastly, you may have a failing CCD. As such, a repair may be your only recourse. And if you still have a warranty, your best bet is to get it to Olympus ASAP to have it repaired under the warranty.