Ok, time to re-post what I already wrote, but later edited, and replaced with what's currently in my last post...:brows:
The way I see it, you have two options now:
One, to use Grub without the stage 1.5 file (which is possible only if the boot partition for Linux is not above the 1024 cylinder threshold...roughly 8GBs, which unfortunately, your Ubuntu partition is well beyond that because it is the third partition on the disk). If you choose this method, you will need to either reinstall Ubuntu, or delete your first partition, and create a new one (it only needs to be big enough to store Grub), formatting it as ext3, copy the "boot" folder over into that partition, set it to "active", and use it as your boot partition. Probably not something you want to do...
The other option is actually only a possibilty, because I don't know if its true or not. But, reading
this link, I found mention of the possible cause of why your stage 1.5 file is failing you. This file is stored at sectors 2 to about 16 (the first partition starts at sector 63, the MBR is the first sector), and exists between your MBR and first partition, on the disk. After reading that link, I came across information that may explain your problem. According to "MPH", there are at least two Highpoint ATA controllers, the Y2K era HPT366 chip and the RocketRAID 152x SATA Host Adapter,
which write on the first track of a hard drive just like GRUB stage 1.5 does. The latter controller’s manual (
http://www.highpoint-tech.com/PDF/RR1522a/RR152x_User_Manual.pdf) states, “For SuSE 10.x, please format the /boot partition using ext3 format (default is reiserfs). Otherwise, the GRUB boot loader will overwrite the RAID information stored on sector 9 and cause your RAID array to be broken”.
If that is the truth, it means data is being written by your harddrive controller
in the same place that stage 1.5 is stored, meaning it is getting corrupted. Now what MPH did in the scenario, is he moved the stage 1_5 file out of the /boot/grub folder, and in a different location (in case he needed it later on), and reinstalled Grub to the MBR, which he said allowed him to boot.
But, there may be some way to stop your hard drive controller from writing to that location on the disk, but that it is a very slim possibilty at best.
Not a whole lot else for you in terms of options, that I see...
Jake