Repeated MBR corruption on ICH6 machine

I have an Acer 4100WLMi laptop (spec at http://surrey.lug.org.uk/cgi-bin/wiki.pl?TravelMate4100WLMi ) I have increased the RAM from thsi spec to 1.25GB.

I have had 4 incidences of the MBR on my boot drive (hda) ceasing to be readable (BIOS produces "Operating System Not Present" error at bootstrap)

I installed wine (0.9.9-0ubuntu2) then installed DVD Decrypter 3.5.4.0 and DVD Shrink 3.2. I recreated the DOS device for the DVD drive and selected NT4.0 as Mr.Bass says. I now have 2 problems:

1) Neither DVD Decrypter nor DVD Shrink can see the DVD drive (hdb). I tried using hdb=ide-scsi but then nothing could see it!

2) This is the bad one... When I go into DVD Decrypter and try the different IO optons to scan for the DVD drive the MBR of hda gets trashed (BIOS reports "No Operating System Found" at bootstrap) and I have to boot off the an install disc and do a "grub-install hda" to to make the drive bootable again. Here's what I know or suspect.

    * My machine is an Acer Travelmate 4100WLMi with an Intel ICH6 chipset
    * Every time this has occured I have been performing an activity with the DVD drive.
    * I have had this happen twice in Ubuntu Dapper (once with DVD Decrypter, once burning a DVD with nautilus) and twice with MEPIS 6.0 so I would suspect that it is related to one of the common Ubuntu components between the distros.
    * The DVD drive is hdb so it shares a bus with the HDD
    * This never happened with Breezy so it's probably something that changed between Breezy and Dapper.
    * On boot there is a string of about 9 errors something to do with not being able to allocate a region of the PCI bridge (I think the messages were that region 7,8,9 could not be allocated from 0000:000:1c.0,1,2 but they happen before logging starts so never get written in the logs.)
    * I'm doing this from a mortal user account so I shouldn't be able to write the MBR. I therefore suspect either a kernel or IDE driver bug.

These are the only abnormal entries I found in messages at about the right time but I think they're not relevant:
Oct 18 10:07:14 localhost kernel: [17179916.948000] ABORTED IN=eth0 OUT= MAC=00:
c0:9f:91:2f:ea:00:80:42:11:27:21:08:00 SRC=3.44.123.122 DST=3.4.208.108 LEN=54 T
OS=0x00 PREC=0x00 TTL=255 ID=23069 DF PROTO=TCP SPT=80 DPT=3885 SEQ=3159725861 A
CK=0 WINDOW=32768 RES=0x00 RST URGP=0
Oct 18 10:07:16 localhost kernel: [17179918.248000] ABORTED IN=eth0 OUT= MAC=00:
c0:9f:91:2f:ea:00:80:42:11:27:21:08:00 SRC=3.44.123.122 DST=3.4.208.108 LEN=54 T
OS=0x00 PREC=0x00 TTL=255 ID=23079 DF PROTO=TCP SPT=80 DPT=1495 SEQ=756608386 AC
K=0 WINDOW=32768 RES=0x00 RST URGP=0