Bug#382689: Acknowledgement (debian-installer: d-i etch beta3 tries to access /dev/md/0p1)
I just had the same problem again, so here is the important part
of the error message:
Error informing the kernel about modifications to partition
/dev/md/0p1. This means ... blah blah.
Pressing [Cancel] shows another error message:
The kernel was unable to re-read the partition table on /dev/md/0
(Invalid Argument). ...blah blah...