Ok.

It seems that fsck doesnt really solve the problem. Weird kernel errors
may pop up upon bootup.

I've tried popping in SLAX live cd. But oftenly, even SLAX can fail to
boot up the system with weird init errors.

I realised it would be a problem with my ram.

I removed one stick of ram from my system. That solved the problem. I
can boot up with no issues.

That stick of removed ram is higly suspicious. Im wondering are there
any ram testing tool in linux