E6430 is not turning on with 100% working RAM

Hi.

I'm looking for any kind of help here, because the whole story is a mystery to me. I tried to upgrade my RAM by installing two new modules, but the laptop stopped turning on after that (well, it does turn on, but nothing happens, the screen in black, the indicators don't blink, and it turns off by itself after a few seconds).
So I returned the original RAM and got the same result (I tested it on my other laptop, it works). After hours in Google I learned about CMOS battery. I removed it, put it back, turned on the laptop and it helped, I got to BIOS. So at that point I solved my problem. But...
Unfortunately, I decided to repeat the same trick with the new modules. It didn't work out. So I installed the old RAM again, and now I can't make it work. I tried to remove the CMOS battery several times already, but it doesn't help. When I press the power button, the laptop turns on, the screen is still blank, and after few seconds in turns off. The HDD indicator lights on and the battery indicator blinks.

So the resume: at this point all the hardware is 100% good and compatible, but it's not turning on properly. Can anybody help me with this? I don't know what to do anymore.