Z77 Extreme4 won't stay asleep

[HardwareFailureGuy]

I'm having a weird problem with "sleep" mode in a system built with an ASRock Z77 Extreme4 motherboard, and I'm wondering whether it's motherboard-related, because it didn't happen when I was using a different motherboard.

Essentially, the system has to be placed in "Sleep" mode twice, or it doesn't stay asleep. If I am using Windows 7 and invoke the "Sleep" command, or just let it enter "Sleep" automatically through power management settings, the machine doesn't stay that way. After around 1 minute, the system will mysteriously start up, even though I haven't touched the mouse, keyboard, or anything else.

I then have to log in (I have a password on my user account) and enter "Sleep" mode manually once more, or the system will just sit at the Windows 7 login screen forever.

Maybe there's a BIOS setting I missed somewhere? I'm using exactly the same hardware I was using with a Gigabyte board (GA-Z77-DS3H) which didn't require being told to "sleep" twice.

FWIW, I do have Hybrid Sleep enabled in the advanced Windows 7 power settings. I tried turning it off and entering "Hibernate" instead, but I get the same result - the system wakes itself for no apparent reason, and has to be placed in Hibernate a second time.

I also went into Device Manager and turned off the ability of the mouse to wake the system under its power-settings tab.

So what's going on here?

eta:
This also may help: I uninstalled the ASRock Instant Boot utility. I don't think I can use it anyway, since I have a password on my user account. Is it possible some piece of that utility is still there, and is somehow causing the machine to wake itself?

[HardwareFailureGuy]

Apparently this was a problem with "Wake on LAN." It was turned on by default in my network adapte settings.

This board's BIOS doesn't have a setting for Wake on LAN, which is why I didn't find it earlier.

[CRRacer]

Sounds about right. Although my machine with this same mother board stays in hybernate until the server calls on it for a backup.

Most often it works fine, but I noticed this morning that the driver for the wireless adapter must have hung because the backup failed and the wireless adapter was busy, but the machine was locked up (or busy with whatever was going n with the wireless adapter.