Very strange issue, machine turns on by itself

Machine is set to sleep mode, goes to sleep at the set time of 30 minutes, case power light is off, fans off.
At about 5 minutes re-start and then turn off right away, power light stays on, fans stays off.
Inboard IR doesn't turn machine on by remote, can turn on and off before case power light stays on.
Every 10 minutes start and turn off right away. All this while network cable is connected I can only turn machine on by power button If I disconnect the LAN cable, machine stays in sleep mode and case power light is off. Machine can be turn on by IR remote, wireless keyboard or power button

All this happens while the rest of my machines are off, therefore I don't think is been turned on by a packet

This are the settings I can find related to LAN, unless there is some settings hidden somewhere.

At BIOS in power settings: After Power Failure (Stay off)
Wake on LAN from S5 (Stay off)
ACPI Suspend State (S3 State)
EIST (Enable)
Wake system from S5 (Disable) At OS: Intel Gigabit Ethernet Adapter: Power Management:
Power saving options:
All 3 boxes checked
Wake on LAN:
All 3 boxes unchecked
Specs: M/B Intel DG45ID, CPU Intel e 7200, 2GB A-data Mem
1 Sata HDD, Sata BD player
OS: Vista Ultimate 32

Network is set as follows: Cable Modem to D-Link 524 router:
2 wireless PCs: 1 Win XP
1 Dual boot XP/Vista
3 wired PCs: 2 Win XP
1 Vista
Xbox 360

I am only having this issue with this specific machine.
Now if I remove the network cable from the router and install a crossover cable between two machines everything works as supposed.

Thanks in advance for your help

Luis