SD-EXT file system damaged in a few days

I'm running an cooked Android on my HD2 with the sd-ext partition trick to increase storage space. I noticed that with more than just one ROM that file system gets corrupted in a very short time. In a few days of running the FS gets so corrupted that Android itself can't boot. I have to fsck from my Linux machine and get lots of lost files before turning the phone on again (and every time I lose something). While the obvious answer (I actually haven't asked anything yet) may seem to "try another ROM", my question is: what could be causing this corruption of the file system as soon as I **always** turn off my phone the clean way? Could it be some program running on top of Android? Unbelievable, Linux kernel handles file system internally. AFAIK, virtually no app can damage a file system if only operating with file read and write Could it be the Android kernel? Could it be the specific data2sd script that I install from recovery? I don't think so because what it does is to merely install an init script that runs once per boot and mounts the card. I'm asking if anyone here had the same problem, and if and how he/she managed to fix it.