MBP Freezing after 10.5.3 Update

I have a previously perfectly functioning MacBook Pro 2.4GHz, however, after updating to Leopard 10.5.3 I am experiencing occasional sudden freezes where the mouse and keyboard are completely unusable. Even plugging in an external keyboard and mouse is unresponsive. The only fix is a hard power-off.

Anyone else seeing this?

Cliff.

What are your system specifications? Are you running any third party enhancements (haxies)?

The extensions I'm using which are additional to OS X are:

APE (2.5b1)/WindowShade X 4.2b1
Growl
USB Overdrive
Flip4Mac WMV
Keyclick

Here's a representative process list, not sure this is the mix which causes the freeze but it's quite typical:

4223 Activity Monitor cliff 7.6 7 27.41 MB 990.36 MB Intel
3019 Safari cliff 1.3 14 99.25 MB 1.01 GB Intel
160 Finder cliff 1.1 9 88.36 MB 1.04 GB Intel
2926 Mail cliff 0.3 15 129.31 MB 1.06 GB Intel
202 Microsoft Messenger cliff 0.3 10 27.08 MB 967.48 MB Intel
3025 Microsoft Word cliff 0.3 7 187.40 MB 1.15 GB Intel
158 SystemUIServer cliff 0.2 14 20.68 MB 935.87 MB Intel
196 iChat cliff 0.2 13 73.82 MB 1.04 GB Intel
195 USBOverdriveHelper cliff 0.1 2 3.58 MB 900.73 MB Intel
3004 iTunes cliff 0.1 6 36.39 MB 975.70 MB Intel
155 Dock cliff 0.1 5 27.53 MB 950.89 MB Intel
165 CNQL4801_ButtonManager cliff 0.1 2 3.16 MB 851.96 MB Intel
3029 Microsoft Database Daemon cliff 0.1 3 10.85 MB 920.23 MB Intel
207 MenuCalendarClock iCal cliff 0.0 8 14.51 MB 923.37 MB Intel
206 Image Capture Extension cliff 0.0 3 5.61 MB 878.40 MB Intel
140 launchd cliff 0.0 3 568.00 KB 585.74 MB Intel
194 Quıcĸsıɩⅴεʀ cliff 0.0 3 59.12 MB 985.68 MB Intel
2964 QuickTime Player cliff 0.0 6 20.61 MB 964.30 MB Intel
201 NETserver cliff 0.0 2 2.98 MB 851.43 MB Intel
156 ATSServer cliff 0.0 2 15.37 MB 664.27 MB Intel
4207 System Profiler cliff 0.0 3 26.12 MB 947.50 MB Intel
310 Alerts Daemon cliff 0.0 4 6.67 MB 900.57 MB Intel
223 Microsoft Messenger Daemon cliff 0.0 3 3.18 MB 851.97 MB Intel
214 GrowlHelperApp cliff 0.0 6 26.11 MB 954.04 MB Intel
316 AppleSpell.service cliff 0.0 1 3.79 MB 601.72 MB Intel
144 AirPort Base Station Agent cliff 0.0 4 5.10 MB 910.35 MB Intel
2991 TextEdit cliff 0.0 3 16.56 MB 931.64 MB Intel
154 aped cliff 0.0 1 1.14 MB 586.77 MB Intel
215 Growl Menu cliff 0.0 2 6.30 MB 911.15 MB Intel
220 ControlCenter cliff 0.0 2 11.24 MB 925.86 MB Intel
3028 Microsoft AU Daemon cliff 0.0 2 3.29 MB 868.05 MB Intel
4222 PubSubAgent cliff 0.0 2 1.49 MB 589.14 MB Intel
148 Spotlight cliff 0.0 3 7.15 MB 880.32 MB Intel
166 LOGINserver cliff 0.0 2 2.96 MB 851.38 MB Intel
149 UserEventAgent cliff 0.0 2 2.79 MB 846.37 MB Intel
3217 ColorSync Utility cliff 0.0 3 9.69 MB 923.68 MB Intel
63 loginwindow cliff 0.0 3 9.68 MB 936.41 MB Intel
222 iChatAgent cliff 0.0 3 9.31 MB 862.93 MB Intel
4160 mdworker cliff 0.0 4 8.79 MB 638.96 MB Intel
208 Preview cliff 0.0 6 27.79 MB 978.75 MB Intel
192 USBserver cliff 0.0 2 2.91 MB 851.38 MB Intel
150 pboard cliff 0.0 1 588.00 KB 586.64 MB Intel