Tell me what you mean by "the same problem". I've managed to solve my issue.
If you get the errors I mentioned in post #10, I first followed the procedure mentioned in post #9. That took away the errors, when removing one of the disks, but still didn't allow the system to boot from either one of them. If the two disks were present, everything worked OK, but with one disk only, the system didn't boot. The message showing which kernel would load was shown, but the system was rebooting the PC from scratch, from the BIOS screen.
By carefully studying the grub.conf, I noticed that the system was trying to boot the kernel from hd1, which I believe doesn't exist when only one disk is present. So I edited grub.conf and changed every reference to hd1 to hd0. That allowed the system to boot, even when only one disk was present. I tried with either disk and both booted fine. When I connected both disks again, the system also booted fine, but it seemed that the arrays were not correct. I then used mdadm to re-add the missing partitions to the raid devices and everything worked just fine and I had a full working system, with a working RAID 1 array, able to boot from either disk.
It took me a while fighting the various issues of the RAID but I think it is something well-worth it, since it adds a significant feature to my system and gives me some peace of mind.