I'm taking seriously into consideration buy a new one, I don't want to wait until the drive is utterly broken.
And yes, I have heard lite-on drives are very reliable. 😎

Done. I have just got my hands on a Plextor PX-116A3 drive. It still make some pause (1 sec or so), but at least the system doesn't stop responding. It is also UDMA4.

Damnit. I discovered this by chance. Increasing PCI Latency in bios (clock ticks) from the default 32 to 64 seems to have fixed the problem. Only if I had would known before... 😢