TI89 frozen, keys ignoring, no OS, no busy, no reset

[oborovgn]

Hi,
my TI89 (no titanium) is frozen, doesn't respond to any button, and it won't turn off. It didn't happen while I was using it, but that's how I found it after a week I didn't use it: it was on, on home screen with my last work session and totally frozen: the cursor of the command line doesn't even blink and the TI89 it's not on "busy".
Normal reset (ON+SHIFT+LEFT+RIGHT) didn't work (no respond from the buttons), and total reset [ (-) + ) during power on ] worked, meaning that it reset the TI89 deleting all data and the screen settings, but the calculator is frozen like before. I even removed the backup battery with no success.
The only thing the TI89 seems to respond is the connection with the PC (usb cable) which seems to be the only thing that can inteact with the calculator making the display changing etc...
So I tried reinstalling the OS but after the successful installation the TI89 is still frozen!
My limited conclusions:

1) If the keyboard was somehow damaged I couldn't have reset it with (-) + ) during power on . Note I know it's reset cos it deleted also all files.

2) If it was an OS problem I should have solved it reinstalling the OS, nothing changed.

So, what can I do? What could be the problem? I never installed harmful programs or games, only official apps from Texas Instrument.

If there is someone out there who have a clue or advice, please help me!
thank you

Obo

OS vers.: 2.09
BIOS vers: 1.07

[F77]

Take compressed air or your lips and blow gently into the USB port on the top right side of the calculator and then try it.

Then 2nd and off and it worked for me. Didn't turn back on immediately until I pushed the "On" button again either.