System will not shut down - Immediately restarts *updated*

When shutting down the system with the start menu, it logs off and almost shuts down. Then it immediately restarts. The restart is not a normal restart, as it seems to completely power-off before restarting.

 

It will also "wake up" when trying to enter sleep mode.

 

This will happen repeatedly until I shut down by holding the power button, or reboot into Safe Mode. If I log off first before shutting down, it makes no difference...the problem still occurs.

 

 This is not a "blue-screen" automatic restart, and the problem occurs with the wireless router on or off.

 

 If I re-boot into Safe Mode without networking (by hitting F8 when the system restarts) it ALWAYS shuts down without a problem.

 

The problem is intermittent, and many days can go by with normal shutdowns.

 

I have studied the event viewer, and found nothing conclusive.

 

Has anyone solved this problem?

 

Thanks!

 

UPDATE:

After months of testing, I finally narrowed it down to the wireless network connection. As long as I disable the connection prior to attempting shutdown, the system shuts down normally.

 

If the wireless connection is enabled at the time of shutdown (even if it’s disconnected from the network), the computer immediately powers back on.

 

I updated the driver, but it made no difference.

 

The network card is a D-Link DWA-556 Xtreme N PCIe desktop adaptor (802.11n). Driver version 7.4.2.87, dated 7/2/2008

 

 

System Info:

Dell Inspiron 530s, 4GB RAM, Intel Core 2 Duo CPU E4500 2.20 GHz.

Windows Vista Home Premium, SP-1 

 

Bluetooth mouse and keyboard