I've a Powermac7,2, Dual1.8GHz, Firmware 5.15f0, which has following issue running MorphOS_3.12:

After boot.img is booted from boot-partition(HFS), he does'nt see the complete HD anymore (where he booted from!!!)- and booting stops. They partitions even don't occur in early-startup-menue.....
In the past boot.img_3.12 booted through after several reboots (sometimes even on the first attempt), but then it needs more and more reboots, and now no chance.
If I use on the same HD (nothing changed) but boot.img from MorphOS3.11, every partition (SYS, WORK,...etc.) can be seen after booting (but no complete booting, because boot.img 3.11 is too old for the 3.12 installation, of course).
On 5th partition, MacOS X is located, which also boots without any problem.

I've now switched back to MorphOS3.11, but thats not really satisfying, because I have to switch back OWB, VPDF and have no temperature-control......
Btw.:
Tested this with a plain installation on a CF-Card (2nd.ide.device) too: the same behaviour. Seems really depending on boot.img. On my other PowerMACs (7,3) are no such issues, but they have a newer firmware (5.18f7, 5.24f1).....!?!

Any ideas?