What Hardware version is your router? Look at sticker under router.
Link>What
Firmware version is currently loaded? Found on routers web page under status.
What region are you located?
Is the Modem bridged and is the 655 using PPPoE for establishing a Internet connection to the ISP? If this modem has a built in router, it's best to bridge the modem. Having 2 routers on the same line can cause connection problems.
Double NATTo tell if the modem is bridged or not, look at the routers web page, Status/Device Info/Wan Section, if there is a 192.168.0.# address in the WAN IP address field, then the modem is not bridged.
If the modem can't be bridged then see if the modem has a DMZ option and input the IP address the router gets from the modem and put that into the modems DMZ.
I might review this over on DSL reports if you can't get these 2 to connect:
http://www.dslreports.com/faq/7125I might do a factory reset on the 655 and set it up for PPPoE again and see.
Also check with you ISP on MTU settings, most DSL uses 1492 down to 1472. Check with the ISP to be sure.
Let us know...