Internet Connection Problem???

[John S]

Why not simpify things.. Your Pre-N Router should have DHCP on it and probably at least 1 LAN port..right?
If so, take out the Linksys Router altogether and use the Pre-N Router as both the DHCP and WAP

Thus
modem-->Pre-N-->Switch

I had this issue 2 when trying to switch a D-Link Di-524 Wireless router as just a switch.. things would work for about 10 minutes then Zero traffic would get thru the D-Link to the primary router.
I finally solved the issue by using another Router I have and converting THAT to a switch instead.

Not sure what you are trying to say about the "Default Gateway sign on to Wired Router"
Any router can act as a default gateway, the modem doesn't care (or shouldn't care) as long as it is rebooted and gives out only 1 IP, it will give that IP to any computer or router that requests it.