i had a problem similar to this once before, you might want to check with your ISP. Sometimes a problem on there end can also disconnect you, im not sure if youv tried that as an option or not but call them up and see what going on there, if you still have problems....then i have no idea lol sorry, butp calling my ISP usually fixed this problem on my end.

i just did a lil searching and foun a big list of how tos that may help you also, im sorry i cant help more but hopefully you find the problem

http://www.linux.org/docs/faq.html