It tries to find sda1 and sda5 before going into a kernel panic, however, it does sometimes give me this:

For which I have no explanation whatsoever. 
Before changing the MB, was the system running properly? I'm thinking there may be a bad connection to the hard drive in either the power or data cable. If you have spares, try a different data cable. If not try disconnecting from both ends and reconnecting. Also disconnect and reconnect the power cable to the hard drive. The files are there, but the kernel can't seem to read the data.
The other thing to try is a forced fsck on the
/ partition. From the
terminal on the
liveCD, with the
/ partition unmounted, as
root;
[root@localhost ~]# umount /dev/sda1 <Enter>
[root@localhost ~]# fsck -f /dev/sda1 <Enter>
Post the result of the
second command.
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FYI:Most of my installations are on
external hard drives, connected by either
eSATA when available, or
USB2. I move these from one computer to another, some my own, some belonging to friends. Obviously,
different MBs are involved with each move, yet
none of the installations
fail to boot properly. At worst I get notified that new hardware was found, and I'm then asked if I wish to configure that new hardware. I say yes, the job gets done, and I'm good to go. You should be getting a single, similar experience, from the MB change, and nothing more, assuming all connections are proper, the memory cards have full contact, and the video card is fully seated, if it's an add-in card.