External monitor stopped working after 10.6.7 update

Question

I have a MacBook Pro, model identifier MacBookPro6,2 with an NVIDIA GeForce GT 330M.
When I updated last night from 10.6.6 to 10.6.7 I stopped being able to use my Dell S2409W external monitor.
I have tried resetting the pram, resetting the SMC, booting with extensions off.
When I plug in the cable to the external monitor the Mac screen goes blue for about 0.5 second and re-appears but nothing displays on the external monitor; a second monitor is not listed in the Display preferences and the monitor reports that it is not receiving a signal.
I don't see anything in the system.log when I plug or unplug the monitor cable (I'm not sure if I should).
At random intervals while the external monitor cable is plugged in the screen goes blue for a half second and then re-appears.
The screen does not go blue if I wiggle or flex the monitor cable.

Answer 1

I see this in the windowserver.log after reboot, login with shift-key, and the external monitor connected.
There might be a clue here but I don't have anything to compare it to since I haven't collected these data when the external monitor was working.
I'd be curious to see the same data from the windowserver.log for somebody else with a MacBook Pro with an external monitor connected that does work.
You can view this log with the console application located: /Applications/Utilities/console.
If you are willing to share these data please reboot, and hold the shift-key down when logging in to disable extensions (thanks). If you look at the time just when the desktop appears when you end up looking at the windowserver.log you'll be able to see the windowserver starting up about 10 seconds prior to this time.
Mar 22 21:31:26 [110] Server is starting up
Mar 22 21:31:27 [110] CGXMappedDisplayStart: Display0 : boot screen
Mar 22 21:31:27 [110] CGXMappedDisplayStart: Display0 : display alias 0x0 valid
Mar 22 21:31:27 [110] CGXMappedDisplayStart: Display1 : no display alias property
Mar 22 21:31:27 [110] CGXMappedDisplayStart: Display2 : display alias 0x0 valid
Mar 22 21:31:27 [110] MPFinalizeInitialization: Display 0x3f003e unit 2 alias mask 0x5
Mar 22 21:31:27 [110] MPFinalizeInitialization: Display 0x4272dc0 unit 0 alias mask 0x5
Mar 22 21:31:27 [110] GLCompositor: GL renderer id 0x01022612, GL mask 0x00000003, accelerator 0x00003137, unit 0, caps 0x00000003, vram 512 MB
Mar 22 21:31:27 [110] GLCompositor: GL renderer id 0x01022612, GL mask 0x00000003, texture units 8, texture max 8192, viewport max {8192, 8192} extensions 0x0000000f
Mar 22 21:31:27 [110] GLCompositor: GL renderer id 0x01024300, GL mask 0x00000004, accelerator 0x00003c0b, unit 2, caps 0x00000003, vram 288 MB
Mar 22 21:31:27 [110] GLCompositor: GL renderer id 0x01024300, GL mask 0x00000004, texture units 8, texture max 8192, viewport max {8192, 8192} extensions 0x0000000f
Mar 22 21:31:27 [110] agc_attach: gMux mode is dynamic
Mar 22 21:31:28 [110] CGXPerformInitialDisplayConfiguration
Mar 22 21:31:28 [110] Display 0x4272dc0: MappedDisplay Unit 0; Vendor 0x610 Model 0x9cb7 S/N 0; online enabled built-in (0,0)[1680 x 1050], Rotation 0, base addr 0x102a00000
Mar 22 21:31:28 [110] Display 0x4272dc2: MappedDisplay Unit 2; Vendor 0x610 Model 0x9cb7 S/N 0; offline enabled built-in (2704,0)[1 x 1], Rotation 0, base addr 0x113800000
Mar 22 21:31:28 [110] Display 0x3f003d: MappedDisplay Unit 1; Vendor 0xffffffff Model 0xffffffff S/N -1; offline enabled (2705,0)[1 x 1], Rotation 0, base addr 0x102a00000
Mar 22 21:31:28 [110] Display 0x4272dc0: MappedDisplay Unit 0; ColorProfile "Color LCD" (MD5 a23cb9c96f2fd096b7a058db0d319259)
Mar 22 21:31:28 [110] kCGErrorIllegalArgument: CGXSetWindowListTags: Operation on a window 0x2 not owned by caller (PID 202)
Mar 22 21:31:35 [110] kCGErrorIllegalArgument: CGXSetWindowListTags: Operation on a window 0x2 not owned by caller (PID 206)