Machine is running an up-to-date Fedora 17 and has a 9600GT card:

https://bugzilla.redhat.com/show_bug.cgi?id=850573

I have an LG 44NHM84 TV connected to the second DVI port of a GeForce 9600GT card using a DVI-to-HDMI cable and an HDMI switcher. If I switch the switcher for the TV to the computer input, the main monitor loses signal as well as the TV, and dmesg reports the following:

Sep  8 23:12:54 newcastle kernel: [1467414.791946] detected fb_set_par error, error code: -16
Sep  8 23:12:54 newcastle kernel: [1467417.024758] [drm] nouveau 0000:01:00.0: GPU lockup - switching to software fbcon
Sep  8 23:12:57 newcastle kernel: [1467420.791069] [drm] nouveau 0000:01:00.0: Failed to idle channel 2.

Xorg also segfaults with the following backtrace:

#0  0x0000003425435925 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x00000034254370d8 in __GI_abort () at abort.c:91
#2  0x000000000046c86e in OsAbort () at utils.c:1207
#3  0x0000000000482d6c in ddxGiveUp (error=EXIT_ERR_ABORT) at xf86Init.c:1009
#4  0x0000000000468ef2 in AbortServer () at log.c:476
#5  0x00000000004690f5 in FatalError (f=f@entry=0x572db8 "Caught signal %d (%s). Server aborting\n") at log.c:611
#6  0x000000000046a2de in OsSigHandler (sip=<optimized out>, signo=11, unused=<optimized out>) at osinit.c:146
#7  OsSigHandler (signo=11, sip=<optimized out>, unused=<optimized out>) at osinit.c:107
#8  <signal handler called>
#9  0x00007f1be12f222b in ?? () from /usr/lib64/xorg/modules/drivers/nouveau_drv.so
#10 0x00007f1be0269e66 in exaDoPutImage (src_stride=<optimized out>, bits=0x61fc168 "$\025\f", format=2, h=34, w=1920, y=1920, x=34, pGC=0x3acab10, pDrawable=0x3b463b0, 
    depth=<optimized out>) at exa_accel.c:212
#11 exaPutImage (pDrawable=0x3b463b0, pGC=0x3acab10, depth=24, x=0, y=34, w=1920, h=34, leftPad=0, format=2, bits=0x61fc168 "$\025\f") at exa_accel.c:233
#12 0x0000000000505452 in damagePutImage (pDrawable=0x3b463b0, pGC=0x3acab10, depth=24, x=0, y=34, w=<optimized out>, h=34, leftPad=0, format=2, pImage=0x61fc168 "$\025\f")
    at damage.c:795
#13 0x0000000000431053 in ProcPutImage (client=0x2aa76a0) at dispatch.c:1963
#14 0x000000000043444a in Dispatch () at dispatch.c:428
#15 0x0000000000423485 in main (argc=13, argv=0x7fff2f6d7948, envp=<optimized out>) at main.c:288

See the possibly related Fedora bug report here: https://bugzilla.redhat.com/show_bug.cgi?id=850573

Nouveau dmesg output from boot:
[    3.535300] [drm] nouveau 0000:01:00.0: Detected an NV50 generation card (0x094100a1)
[    3.539647] [drm] nouveau 0000:01:00.0: Checking PRAMIN for VBIOS
[    3.598564] [drm] nouveau 0000:01:00.0: ... appears to be valid
[    3.598564] [drm] nouveau 0000:01:00.0: Using VBIOS from PRAMIN
[    3.598566] [drm] nouveau 0000:01:00.0: BIT BIOS found
[    3.598567] [drm] nouveau 0000:01:00.0: Bios version 62.94.82.00
[    3.598571] [drm] nouveau 0000:01:00.0: TMDS table version 2.0
[    3.598902] [drm] nouveau 0000:01:00.0: MXM: no VBIOS data, nothing to do
[    3.598906] [drm] nouveau 0000:01:00.0: DCB version 4.0
[    3.598910] [drm] nouveau 0000:01:00.0: DCB outp 00: 02000300 00000028
[    3.598913] [drm] nouveau 0000:01:00.0: DCB outp 01: 01000302 00020030
[    3.598915] [drm] nouveau 0000:01:00.0: DCB outp 02: 04011310 00000028
[    3.598918] [drm] nouveau 0000:01:00.0: DCB outp 03: 02011312 00020030
[    3.598920] [drm] nouveau 0000:01:00.0: DCB outp 04: 010223f1 00c0c083
[    3.598922] [drm] nouveau 0000:01:00.0: DCB conn 00: 00001030
[    3.598926] [drm] nouveau 0000:01:00.0: DCB conn 01: 00002130
[    3.598928] [drm] nouveau 0000:01:00.0: DCB conn 02: 00000210
[    3.598931] [drm] nouveau 0000:01:00.0: DCB conn 03: 00000211
[    3.598933] [drm] nouveau 0000:01:00.0: DCB conn 04: 00000213
[    3.598938] [drm] nouveau 0000:01:00.0: Parsing VBIOS init table 0 at offset 0xD681
[    3.624214] [drm] nouveau 0000:01:00.0: Parsing VBIOS init table 1 at offset 0xDAE7
[    3.627125] [drm] nouveau 0000:01:00.0: Parsing VBIOS init table 2 at offset 0xEAE8
[    3.627133] [drm] nouveau 0000:01:00.0: Parsing VBIOS init table 3 at offset 0xEC09
[    3.628217] [drm] nouveau 0000:01:00.0: Parsing VBIOS init table 4 at offset 0xEF24
[    3.628219] [drm] nouveau 0000:01:00.0: Parsing VBIOS init table at offset 0xEF89
[    3.648185] [drm] nouveau 0000:01:00.0: 0xEF89: Condition still not met after 20ms, skipping following opcodes
[    3.652467] [TTM] Zone  kernel: Available graphics memory: 2023556 kiB
[    3.652469] [TTM] Initializing pool allocator
[    3.652476] [TTM] Initializing DMA pool allocator
[    3.652489] [drm] nouveau 0000:01:00.0: Detected 512MiB VRAM (GDDR3)
[    3.654868] [drm] nouveau 0000:01:00.0: 512 MiB GART (aperture)
[    3.655717] nouveau 0000:01:00.0: irq 55 for MSI/MSI-X
[    3.655728] [drm] nouveau 0000:01:00.0: enabled MSI
[    3.693553] [drm] nouveau 0000:01:00.0: DCB encoder 1 unknown
[    3.693557] [drm] nouveau 0000:01:00.0: TV-1 has no encoders, removing
[    3.695635] [drm] Supports vblank timestamp caching Rev 1 (10.10.2010).
[    3.695638] [drm] No driver support for vblank timestamp query.
[    3.701073] [drm] nouveau 0000:01:00.0: 2 available performance level(s)
[    3.701080] [drm] nouveau 0000:01:00.0: 0: core 300MHz shader 600MHz memory 300MHz fanspeed 100%
[    3.701085] [drm] nouveau 0000:01:00.0: 3: core 600MHz shader 1500MHz memory 900MHz voltage 1010mV fanspeed 100%
[    3.701090] [drm] nouveau 0000:01:00.0: c: core 500MHz shader 1250MHz memory 499MHz voltage 1010mV fanspeed 100%
[    3.749478] [drm] nouveau 0000:01:00.0: MM: using CRYPT for buffer copies
[    3.863834] [drm] nouveau 0000:01:00.0: allocated 1920x1080 fb: 0x2c0000, bo ffff88013955c400
[    3.864024] fbcon: nouveaufb (fb0) is primary device
[    3.883778] Console: switching to colour frame buffer device 240x67
[    3.885833] fb0: nouveaufb frame buffer device
[    3.885836] drm: registered panic notifier
[    3.885841] [drm] Initialized nouveau 1.0.0 20120316 for 0000:01:00.0 on minor 0

Let me know if there is any more information that is needed.