M18X R2 CMOS battery issue

Hi, it's been a few weeks that I've been having issues apparently related to the CMOS battery. Here's what happens:

1. The first time I try to turn the notebook on, the lights turn on and soon after that it shuts down. (It happens both using battery and power source).

2. The second time I turn it on, the lights turn on, the notebook emits five beeps and the screen doesn't turn on.

3. The third time I turn it on, the system boots up normally, and the time and date are reset to 2011/01/01, 00:00.

This process happens whenever I try to turn it on using the battery or when I plug it into a power source (i.e., it was previously unplugged).

Here's what I already tried:

1. Draining out the energy;

2. Updating the BIOS;

3. Replacing the CMOS battery (with and without draining the energy).

4. Pressing Fn while turning the notebook on (no errors detected on the diagnostic system).

5. Booting the system without the CMOS battery (the same 3-step booting cycle happens in this case).

If I boot Windows, fix time/date, shut it down, remove the power cord and reconnect it a few minutes later, Windows is loaded at first attempt (without any beeps), but the time freezes at the moment when I turned the notebook off -- for instance, if I turned it off at 5:00 pm and then turn it on at 5:05pm, the system's clock will show 5:00 pm.

I'm at a loss here -- I thought that replacing the CMOS battery would solve it, but nothing happened, so before I buy another battery, I'd love to hear what you guys have to say about what might be causing it.

Thanks!
Edgard