telnet to router and start pinging your ISP DNS and check for replies. If they're coming back - your WAN port is fine, if they does not probably WAN port is dead. Try executing
then and check if get's recovered.Code:et -i eth1 promisc 1
But for me it does not looks like WAN port dies issue... Something like too many connections or bandwidth is used.
Do you've anything in the system log?
As for port speeds - you've to wait up to minute for connection with fixed speed to be established, this is due to the the fact, thet your modem is unable to negogiate settings, instead it should determine them on it's own.