I have an LED Cinema Display (27"). When I close the lid after plugging the monitor in, the computer doesn't freeze immediately. During the time you'd expect that familiar blue screen to fade in/out, I can still use the mouse, though WindowServer seems to be completely locked up. Then, everything goes poof - computer goes to energy saver mode, no way to wake up, can't even unplug monitor to get things working again.
Here is my system log from when I switched to clamshell up until I got ****** and did a hard reset.
23/9/12 12:23:24.570 PM WindowServer[98]: Display 0x04249f05: GL mask 0x2; bounds (1440, 0)[2560 x 1440], 42 modes available
Active, on-line, enabled, OpenGL-accel, Vendor 610, Model 9226, S/N 160a1686, Unit 1, Rotation 0
UUID 0x0000061000009226160a168600000000, ColorProfile { 3, "LED Cinema Display"}
23/9/12 12:23:24.570 PM WindowServer[98]: GLCompositor: GL renderer id 0x01021b06, GL mask 0x00000007, accelerator 0x0000473f, unit 0, caps QEX|QGL|MIPMAP, vram 1024 MB
texture units 8, texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
23/9/12 12:23:24.876 PM WindowServer[98]: Created shield window 0x77 for display 0x042728c0
23/9/12 12:23:24.876 PM WindowServer[98]: Created shield window 0x78 for display 0x003f003e
23/9/12 12:23:24.892 PM WindowServer[98]: Created shield window 0x79 for display 0x04249f05
23/9/12 12:23:24.900 PM WindowServer[98]: Display 0x042728c0: MappedDisplay Unit 0: Startup Mode 1440 x 900, CGSThirtytwoBitColor, Resolution 1, IOMode 0x43e, IODepth 0x1, IOReturn 0x0
23/9/12 12:23:24.900 PM WindowServer[98]: Display 0x04249f05: MappedDisplay Unit 1: Startup Mode 2560 x 1440, CGSThirtytwoBitColor, Resolution 1, IOMode 0x43e, IODepth 0x1, IOReturn 0x0
23/9/12 12:23:24.908 PM WindowServer[98]: MPAccessSurfaceForDisplayDevice: Set up page flip mode on display 0x04249f05 device: 0x1080c8d30 isBackBuffered: 1 numComp: 3 numDisp: 3
23/9/12 12:23:25.003 PM WindowServer[98]: MPAccessSurfaceForDisplayDevice: Set up page flip mode on display 0x042728c0 device: 0x1080c8320 isBackBuffered: 1 numComp: 3 numDisp: 3
23/9/12 12:23:25.055 PM WindowServer[98]: Display 0x04249f05: GL mask 0x2; bounds (0, 0)[2560 x 1440], 42 modes available
Main, Active, on-line, enabled, OpenGL-accel, Vendor 610, Model 9226, S/N 160a1686, Unit 1, Rotation 0
UUID 0x0000061000009226160a168600000000, ColorProfile { 3, "LED Cinema Display"}
23/9/12 12:23:25.055 PM WindowServer[98]: GLCompositor: GL renderer id 0x01021b06, GL mask 0x00000007, accelerator 0x0000473f, unit 0, caps QEX|QGL|MIPMAP, vram 1024 MB
texture units 8, texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
23/9/12 12:23:25.056 PM WindowServer[98]: Display 0x042728c0: GL mask 0x9; bounds (-1440, 0)[1440 x 900], 39 modes available
Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model 9ca3, S/N 0, Unit 0, Rotation 0
UUID 0x0000061000009ca300000000042728c0, ColorProfile { 2, "Color LCD"}
23/9/12 12:23:25.056 PM WindowServer[98]: GLCompositor: GL renderer id 0x01021b06, GL mask 0x00000007, accelerator 0x0000473f, unit 0, caps QEX|QGL|MIPMAP, vram 1024 MB
texture units 8, texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
23/9/12 12:23:25.056 PM WindowServer[98]: Display 0x003f003e: GL mask 0x4; bounds (3584, 0)[1 x 1], 1 modes available
off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 2, Rotation 0
UUID 0xffffffffffffffffffffffff003f003e
23/9/12 12:23:26.899 PM WindowServer[98]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
23/9/12 12:23:26.904 PM WindowServer[98]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
23/9/12 12:23:26.949 PM WindowServer[98]: Display 0x04249f05: MappedDisplay Unit 1; ColorProfile { 3, "LED Cinema Display"}; TransferTable (256, 3)
23/9/12 12:23:26.950 PM WindowServer[98]: Display 0x042728c0: MappedDisplay Unit 0; ColorProfile { 2, "Color LCD"}; TransferTable (256, 3)
23/9/12 12:23:26.953 PM WindowServer[98]: Display 0x04249f05: MappedDisplay Unit 1; ColorProfile { 3, "LED Cinema Display"}; TransferTable (256, 3)
23/9/12 12:23:26.954 PM WindowServer[98]: Display 0x042728c0: MappedDisplay Unit 0; ColorProfile { 2, "Color LCD"}; TransferTable (256, 3)
23/9/12 12:23:26.969 PM WindowServer[98]: Display 0x04249f05: MappedDisplay Unit 1; ColorProfile { 3, "LED Cinema Display"}; TransferTable (256, 3)
23/9/12 12:23:26.970 PM WindowServer[98]: Display 0x042728c0: MappedDisplay Unit 0; ColorProfile { 2, "Color LCD"}; TransferTable (256, 3)
23/9/12 12:23:26.973 PM WindowServer[98]: Display 0x04249f05: MappedDisplay Unit 1; ColorProfile { 3, "LED Cinema Display"}; TransferTable (256, 3)
23/9/12 12:23:26.974 PM WindowServer[98]: Display 0x042728c0: MappedDisplay Unit 0; ColorProfile { 2, "Color LCD"}; TransferTable (256, 3)
23/9/12 12:23:38.576 PM CalendarAgent[204]: *** -[IADomainCache init]: IA domains cache is out of date.
23/9/12 12:23:46.000 PM kernel[0]: considerRebuildOfPrelinkedKernel com.apple.driver.AppleUSBCDC triggered rebuild
23/9/12 12:23:46.557 PM VDCAssistant[213]: AVF encoder error: fail to create accelerator instance
If anyone can confirm these logs or behavior then maybe we can get something out of this instead of waiting here...