Hello,
This is the last message (on serial), while the Qemu screen is black and empty (it does change its size, so I guess vbeset works, and the failure is in L4/Fiasco somewhere)
Welcome to Fiasco(ia32)! DD-L4(v2)/x86 microkernel (C) 1998-2006 TU Dresden Rev: Thu Nov 23 10:27:00 2006 compiled with gcc 3.4.4 for Intel Pentium Pro Performance-critical config option(s) detected: CONFIG_ASSEMBLER_IPC_SHORTCUT is off
That is a very untypical last message and tells me quite nothing about your problem. However, I have compiled an ISO image for you, which features current binaries, uses GRUB's vbeset, and works with QEMU. You can get it here:
http://os.inf.tu-dresden.de/~nf2/tmp/vbeset-image.iso
You should try out this image using the following command line options to see all debug messages:
qemu -m 64 -serial stdio -cdrom vbeset-image.iso
If this works, compare your menu.lst file against the one on the ISO image. You could also try to successively replace the binaries on the ISO image with your binaries or vice versa.
Good luck! Norman