make kernel -> no root found, sysinstall -> panic

Hi guys,
I cvsupped about two hours ago and made myself a world.  This, on a system
compiled up from 5-CURRENT cvs yesterday, caused a panic when compiling
fork in libc. Not getting through this, I figured the worlds were similar
enough that I compiled up a new kernel and left the world to be compiled
up after boot, just in case. Not a good idea, now it can't find rootvp
when mounting the file systems. Whups...
  Figuring I'm fsck'ed for the moment, I grabbed my CD-RW with 5.1-RELEASE
burned recently and chose Upgrade. Chose Yes, Ok, User, No, Ok, Ok, set my
mount points and chose acd1 to install from. After a short extraction into
/bin, I got the following Panic:

Trap 12: page fault while in kernel mode
fault virtual address = 0x1c
fault code            = supervisor write, page not precent
instruction pointer   = 0x8:0xc02fb3c5
stack pointer         = 0x10:0xd7ba8898
frame pointer         = 0x10:0xd7ba88ac
code segment          = base 0x0, limit 0xfffff, type 0x1b
                      = DPL 0, pres 1, def32 1, gran 1
processor eflags      = interrupt enabled, resume, IOPL = 0
current process       = 41 (bufdaemon)
trap number           = 12
panic: page fault

I'm probably fsck'ed, but I hope this note can help someone if there have
been made any changes lately that have had some significance. :)

Cheers

   Nik