I'm running a small-form-factor PC with an 855GM chipset, and X hangs during startup leaving me with a blank screen on my VGA output.  This happens in 2.4.0 from git, in the current git head (commit 27e9506fda86e90fd67de1715fa32d23aaa8a683), and in 2.3.2-2+lenny1 from Debian sid.  It does _not_ happen in 2.3.2-2+lenny2, and the only difference between those two is that 2.3.2-2+lenny1 includes a cherry-picked patch from 2.4.0 that force-enables pipe A on 855GM, and 2.3.2-2+lenny2 doesn't.

This is the backtrace I get from gdb when attaching to the hung X process (using the git head version of the intel driver):

0xb7b0a5da in i830_crt_detect (output=0x9db1818) at i830_crt.c:285
285             while ((dsl = INREG(pipe_dsl_reg)) <= vsample)
(gdb) bt
#0  0xb7b0a5da in i830_crt_detect (output=0x9db1818) at i830_crt.c:285
#1  0x080f64b0 in xf86ProbeOutputModes (scrn=0x9daf0e0, maxX=2048, maxY=2048)
    at ../../../../hw/xfree86/modes/xf86Crtc.c:1275
#2  0x080f6e24 in xf86InitialConfiguration (scrn=0x9daf0e0, canGrow=0)
    at ../../../../hw/xfree86/modes/xf86Crtc.c:1577
#3  0xb7b15d10 in I830PreInit (pScrn=0x9daf0e0, flags=<value optimized out>)
    at i830_driver.c:1645
#4  0x080ab42f in InitOutput (pScreenInfo=0x8210bc0, argc=3, argv=0xbf9a6f84)
    at ../../../../hw/xfree86/common/xf86Init.c:548
#5  0x08074591 in main (argc=3, argv=0xbf9a6f84, envp=0xbf9a6f94)
    at ../../dix/main.c:369
(gdb)

I'm running the core server version 1.4.2-2 from Debian sid.  I'll attach my config and log.

Cheers.