First of all, most Linksys routers are designed for a broadband connection and can only be connected to a dial-up modem if your modem has an Ethernet port. Please ensure first if your Internet connection is a dial-up connection or a broadband (cable or DSL) connection already.
If you’re in fact using a broadband connection, try the following steps.
First, try adjusting your router’s MTU value to 1492, or 1482…or 1400. If this does not fix your problem, trigger ports 25, 110, 113 on your router’s firewall. Check out this link for guidance:
http://linksys.custhelp.com/cgi-bin/...i=&p_topview=1
This is answer ID 3999 on Linksys’ Knowledge Base. Hope this helps.