Forced Shut Down

After a 1 1/2 years of trouble free MacBook time, I experienced the flashing question mark on startup. The problem proved to be total hard didk and ram failure apparently due to overheating. Now fitted with new 300 GB HD and 2.5GB Ram...worked fine for a few weeks BUT!!! Now I keep getting the forced shut down message ie. "You must shut down...hold the off button for 3 seconds..." The MacBook is then difficult to reboot unless left for a while.
The following error message:

panic(cpu 0 caller 0x0019AB66): interlock timeout for mutex 0x6660040
Backtrace, Format - Frame : Return Address (4 potential args on stack)
0x2ebf3c98 : 0x128d0d (0x3cc65c 0x2ebf3cbc 0x131f95 0x0)
0x2ebf3cd8 : 0x19ab66 (0x3d156c 0x6660040 0x5c10660 0x2000)
0x2ebf3d08 : 0x19832d (0x6660040 0x212 0x2ebf3df8 0x166e3a)
0x2ebf3d18 : 0x166e3a (0x6660040 0x4000 0x0 0x2ebf3dd8)
0x2ebf3df8 : 0x1608eb (0x2ebf3f50 0x4000 0x0 0x5)
0x2ebf3f48 : 0x1a4c3e (0x648c000 0x4000 0x0 0x5)
0x2ebf3fc8 : 0x19b2d4 (0x5d5ef20 0x0 0x19e0b5 0x5d5ef20) No mapping exists for frame pointer
Backtrace terminated-invalid frame pointer 0xb0080be8

Kernel version:
Darwin Kernel Version 8.11.1: Wed Oct 10 18:23:28 PDT 2007; root:xnu-792.25.20~1/RELEASE_I386

Model: MacBook2,1, BootROM MB21.00A5.B07, 2 processors, Intel Core 2 Duo, 2 GHz, 2.5 GB
Graphics: Intel GMA 950, GMA 950, Built-In, spdisplays_integrated_vram
Memory Module: BANK 0/DIMM0, 512 MB, DDR2 SDRAM, 533 MHz
Memory Module: BANK 1/DIMM1, 2 GB, DDR2 SDRAM, 533 MHz
AirPort: spairport_wireless_card_type_airport_extreme (0x168C, 0x87), 1.4.4
Bluetooth: Version 1.9.5f4, 2 service, 0 devices, 1 incoming serial ports
Network Service: AirPort, AirPort, en1
Serial ATA Device: SAMSUNG HM320JI, 298.09 GB
Parallel ATA Device: MATSHITACD-RW CW-8221
USB Device: Built-in iSight, Micron, Up to 480 Mb/sec, 500 mA
USB Device: Bluetooth USB Host Controller, Apple, Inc., Up to 12 Mb/sec, 500 mA
USB Device: IR Receiver, Apple Computer, Inc., Up to 12 Mb/sec, 500 mA
USB Device: Apple Internal Keyboard / Trackpad, Apple Computer, Up to 12 Mb/sec, 500 mA
panic(cpu 0 caller 0x0019AB66): interlock timeout for mutex 0x6660040
Backtrace, Format - Frame : Return Address (4 potential args on stack)
0x2ebf3c98 : 0x128d0d (0x3cc65c 0x2ebf3cbc 0x131f95 0x0)
0x2ebf3cd8 : 0x19ab66 (0x3d156c 0x6660040 0x5c10660 0x2000)
0x2ebf3d08 : 0x19832d (0x6660040 0x212 0x2ebf3df8 0x166e3a)
0x2ebf3d18 : 0x166e3a (0x6660040 0x4000 0x0 0x2ebf3dd8)
0x2ebf3df8 : 0x1608eb (0x2ebf3f50 0x4000 0x0 0x5)
0x2ebf3f48 : 0x1a4c3e (0x648c000 0x4000 0x0 0x5)
0x2ebf3fc8 : 0x19b2d4 (0x5d5ef20 0x0 0x19e0b5 0x5d5ef20) No mapping exists for frame pointer
Backtrace terminated-invalid frame pointer 0xb0080be8

Boot the machine with your original install DVD and run the Apple Hardware Test. See the following LINK.

If the problem is due to overheating, the CPU cooling fan may not be working or running very slow. The AHT should be able to detect that. Also, if the machine's vents are clogged with dirt and the fan is clogged with dirt, that too could cause overheating.

Regards.