The system basics:
Core 2 Duo E4400 (2GHz)
nVidia 6800XT AGP
500W PSU
DVD-RW and DVD-ROM on secondary IDE

When I install one or two IDE drives on the primary IDE, jumpered either as cable select or master/slave, the system boots quickly. When I install one SATA drive, the system boots quickly. But when I install a mix of IDE and SATA drives, the system takes literally several hours to boot.

The system had been running fine for several years with mixed drives until, while I was switching the secondary IDE drive, the cable connector separated from the ribbon. I was able to press it back together and keep going for a little while, but I noticed some problems when booting. I also noticed the SATA1 header bent around this time, but I was able to straighten it and it seems to work fine (when not running mixed drives). I have replaced the IDE cable with one known (or at least highly probable) to be good.

The codes 0075 and 0078 flash quickly, then there is a beep and the screen flashes, then 0085 and 43AC are displayed at the same time, then the screen goes black. With just IDE drives, there is a slight delay, then the system boots. With mixed drives, the system takes several hours (3+) to boot.

I have changed from 2 IDE drives and 1 SATA drive to 1 IDE and 2 SATA, and now I see the following codes: 6B38, 513C, 0075, 0078, then it beeps and flashes as above, showing 0085 and 43AC before going black for several hours.

Is there any hope this could be a configuration problem? Or is this board just going to be unusable for a mixed installation?