Further update, sympotoms:
* I do not think the mouse has anything to do with the problem. It is an INDICATOR of the problem about to happen, but is irrelevant to the problem.
* I am becoming more convinced that it is some tie in between ACPI/APM and the shutdown process. I don't know if eCenter is involved or not.
Why? When the slowdown problem occurs, eCenter:
* Stops registering CPU usage.
* Stops registering Network adapter activity.
* Clicking on the eCS icon in eCenter and selecting shutdown freezes all other objects.
Any attempt to shut the system down to avoid dirty volumes locks out all other objects.
I also tried issuing SHUTDOWN from a command window. The same behavior as using eCenter.
Note: In both cases [eCenter and SHUTDOWN], the expected window with shutdown options does NOT appear. Sometimes, using A-C-D will report, "Shutdown in process..." but with or without that message, the only way to complete the shutdown is to manually POWER OFF with the power off button. And, this requires holding the button down for, what appears to me to be, an excessive interval. i.e., It usually takes about five seconds before the screen goes blank and the indicator lights actually go off.
I don't know if there is any connection, but with ACPI installed and prior to this specific slowdown problem, no matter how I shut the system down, it would not reboot without a manual power off. Using the 'Power Off' option does not work. In fact, any option other than 'Shutdown' results in CHKDSK running due to dirty HDs.
I hope this, along with the log file I posted earlier, provides more clues about the problems I've been having.