Ok, now it won't boot

The installer worked fine (after using Dialog) and the bootmenu reflashed, but when I choose "Deblet on External-MMC-p2" it shows a booting from message for a fraction of a second and then switches to:

Starting linuxrc from deblet-External-MMC-p2 (mmcblk0p2 ext2)...

for about 30 seconds, then the screen gets some off vertical corruption and the tablet reboots back to the bootmenu.

Any ideas?