Strange behaviour of Powershot A620

[embrion]

Hi

I've bought Canon Powershot A620 with infamous E18 error.
It has been fixed but after that fix, the LCD backlight stopped working.
It's rather strange that when I disconnect cables responsible for lens communication then ofcourse I got E18 error displayed again but backlight starts to work also!
Additionally in preview mode I got "no pictures" message which is normal but also I cannot continue to access the menu (button doesn't work)
In record mode lens goes out but after a second aperture (I don't know if I gave a correct name, I mean this little violet dot inside lens) closes itself (BUT I CAN MAKE PHOTOS - aperture opens when I press shutter release button) also I got no live preview on LCD.
No backlight in both modes.
When I connect it to TV via A/V Out then everything is working in both modes:
preview - I can access menu, change options etc
record - aperture doesn't close itself, live preview on TV ,all options available.

I think that some of those ribbons inside the camera could be broken or I might be just a logical error.
Any ideas? I've tried taking off batteries and resetting from menu
Is there any button combination for full factory reset like it was before? (menu button for 5 sec)
Firmware change would reset all settings but I couldn't find any.

=UPDATE=
In Remote Capture program used via USB I can set to clone preview in both computer monitor and LCD in "Camera Display Settings" When I choose that option than LCD starts to preview everything but still without backlight


Greets,
Embrion