system will not power on after shutdown

[sonic6567]

Fresh install of Ubuntu 9.10 (also had issue in 9.04)
Desktop system

From the menu Session -> Shutdown: ShutDown

The system exits and the desktop powers off as expected. (drives spin down, fans shut off, case lights power off, power supply fan stops)

Then press the power button on the desktop and there is no response. (the system should power on)

To fix: Power must physically be removed (unplug power cord from system or toggle off the physical power supply switch on the back of the system) for 5+ seconds then restored. Then the power button will start the system.

This exact desktop with the same hardware configuration using Ubuntu 8.04 did not have this issue.

jdoe@dvdbuntu:~$ lsb_release -rd
Description: Ubuntu 9.10
Release: 9.10
jdoe@dvdbuntu:~$ uname -a
Linux dvdbuntu 2.6.31-17-generic #54-Ubuntu SMP Thu Dec 10 16:20:31 UTC 2009 i686 GNU/Linux

System Information
 Manufacturer: EVGA
 Product Name: 122-CK-NF68
 Version: 2
 Serial Number: 1
 Wake-up Type: Power Switch
 SKU Number:
 Family:
Processor Information
 Socket Designation: Socket 775
 Type: Central Processor
 Family: Other
 Manufacturer: Intel
 Version: Intel(R) Core(TM)2 CPU
 Voltage: 1.7 V
 External Clock: 267 MHz
 Max Speed: 200 MHz
 Current Speed: 2403 MHz
 Status: Populated, Enabled
 Upgrade: ZIF Socket
 L1 Cache Handle: 0x000A
 L2 Cache Handle: 0x000B
 L3 Cache Handle: Not Provided