Installation was on second drive, and grub was installed to the MBR
of that drive. Restart dropped me into grub rescue mode with the
message about normal.mod not being found. After mounting the drive
in Wheezy, I find that the directory that normal.mod is supposed to
be in, is not there. There are only 2 files in /boot/grub - vastly
different from the grub 1.99 of Wheezy!
Try booting from a live CD/USB stick, entering your new installation
in a chroot and running update-grub and grub-install /dev/<your
device>.
I had a lot of similar problems (see recent posts on this list) and
ended up installing lilo instead of grub. The config is much simpler
than grub2.
I have found the upgrade to jessie a painful process - the main
issues being the change to systemd, grub2 and config changes required
in the new Apache. I've almost got everything running properly now.