This will hopefully be useful for someone. I upgraded my CV2 to the newest Nextor Beta 2 and ran in to problems.
Issue 1: after erasing the CV2, I forgot to initialize the CV2. Trying to write the bootblock, I got an error "file not found" and beyond that point, the CV2 was dead, because C2MAN hang. Reboot jumped straight to MSX-Basic because no bootblock.
I created a MSX-DOS 1 bootfloppy with C2MAN, all the required firmware files and booted from that floppy. C2MAN started and I could initialise the CV2. Next I reflashed the boot,IDE and FMPAC parts. CV2 came back to life after reset, but Nextor would find the SD card as master, but jumped straight to MSX-Basic. I remembered that I read that partitions had to be marked active for Nextor to work. So from Basic _FDISK and mark partitions active. My Mac shows 4 partitions on my SD card, and the order is more or less random, so I copied nextor.sys and command2.com to each partition and through trial and error (mark partition 1 active, boot, are the files there?), I discovered that my third partition is the one that contains all my data.
So I short: read the manual and don't forget the initialise step. Otherwise: have a MSX-DOS1 boot disk with C2MAN and required files to save the day.
