As Sammydad1 suggested, the Linksys does have a different IP set (192.168.1.1 as opposed to D-Link's 192.168.0.1).
Either some/most of your PCs are using static IPs, or DNS/WINS cache, etc. is confused by the change. I'd power down all the wireless clients to simplify things. Power down both wired PCs, then power them up one at a time. Check PCs IP with ipconfig and make sure Subnet Mask'd part of each IP Address all match up with routers "SETUP", "NETWORK SETTINGS" page.
Powering everything down and bringing it back up again will likely solve your problem unless you're using static IP addresses, added IP entries to Windows lmhosts file, added IP addresses to Windows "Advanced TCP/IP Settings", etc.
Another thing that can cause this is having more than one DHCP server on the network. If you left the LAN side of the Linksys connected and didn't turn off it's DHCP server it might cause the problem you're having. Could also be your ISP's DHCP messages are getting through the router somehow.