When I was having the problem with my connection it was always the Wireless that would die. I usually restarted everything when that happened and it would work fine for awhile. If I did not go and restart everything eventually the hard line would drop out also. I ended up bringing my wireless access point to work and it has been working perfect since i installed it here (were running DSL).
Not sure if you have access to an apple But i know there is a program for the Mac OS that will tell you what channel all of you neighbors are on, If there are more wireless signals in the area.
There is also 3rd party firmware updates for most of the Linksys line. I think the firmware I was using was called "HyperWap". It let you boost the output of the antenna's and had a few other changes to help it run better.
http://www.linksysinfo.org/forums/fo...play.php?f=138 May be something on there that could help.