You wrote (in your message from  17)
 > I've just upgraded to -current from an older -current from the end of
 > December, and all of a sudden, trying to start XF86_SVGA gives:
 > 
 > | [...]
 > | (--) SVGA: PCI: Matrox MGA 1064SG rev 3, Memory @ 0xe3000000, 0xe0800000
 > | (--) SVGA: Linear framebuffer at 0xE3000000
 > | (--) SVGA: MMIO registers at 0xE0800000
 > | 
 > | Fatal server error:
 > | xf86MapVidMem: Address 0xe0800000 outside allowable range
 > 
 > I've upgraded X as well, but it didn't help.  Any ideas?

Was kernel security level are you running at (look at 'sysctl
kern.securelevel') ?  

If it's not -1, you need to (re)install the XFree86 aperture driver. 
-- 
					Matthieu