Losing my Default Gateway?

I'm having an issue with my default gateway that keeps giving out! I have windows 7 64bit and I noticed when I turn on my torrent or do heavy downloading within mins it gives out. Then I get windows to resolve the issue and it tells me that it fixed the default gateway because it was missing. It seems to disable my lan port and enables it back to fix it and I already swapped out my router thinking it was the issue and used my lan port#2 and still no fix!   I need some help! Please!! Thank u!

run the ipconfig /all command, is the default gateway showing up as zeros?

Are you using a nVidia motherboard and/or network adapter on your Windows 7 system?

If so, see pages 2 and 3 of this thread Repair default gateway every 5 min is getting old
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Have you tried manually setting your default gateway in your adapter preferences?