Try hacking the date FileVersion in the pcb file (hooray for text based file formats) . It might work
Darn - I installed PCB on my system (from the repository), and your version was newer than mine, so it won't load the board; gschem had no problem with the schematic, though.I probably just need to upgrade my system (on Ubuntu 9.10) - I just hate doing it, because it invariably breaks things, then I sit there for a week trying make all my crap work again...
Just had a look at this in a standard installation of pcb and the layer colors are, erm.. interesting. I had forgotten how much my installation was modified.
The only other thing I did was to hack the pcb code & gnetlist scripts to allow 8 trace styles(widths) instead of the standard 4 but that is a whole different ball game for another day.