i have just installed gentoo but have a problem with network and internet.
After installing gentoo, my network card was working properly. Suddenly, something i dont know what it is happened and now
it is not working. I can not connect to internet and can not even ping the computers in my network.

Let me tell my story

I have used the gentoo 2005.0 livecd to install gentoo. At the beginning of the installation, i started my computer with livecd, there was no problem with the network. My computer was able to connect to internet so i have completed the installation without any problem.
And then it was time to restart my computer, and i did. The computer started with the HDD (my linux installed HDD) and i started to use LINUX with pleasure. Then it was time to optimize and setup necessary parts. and i did again. There was not still any problem.After a few steps,suddenly, i could not reach my network and internet. I know it is not a hardware problem. Because when i start my computer with the livecd, there is no problem with network, everything is okey.

I have tried to use dhcp and static ip and as a result of every prefarance, i adjusted necessary files like /etc/conf.d/net
/etc/init.d/net.eth0 . But unfortunately i still could not solve the problem.

Is there any idea to solve this problem?

thanks

can you give us more details about why you "can't reach the internet" ?
What kind of errors messages do you get? Can you ping by ip? Do you see your network card when you type " ifconfig eth0 "?

i can see my network card and also if i get a static ip via editing /etc/conf.d/net file i can see my ip when i type "ifconfig eth0" but i can't reach to the internet... And when i want to get an IP via dhcp i get this error (it's not clear)

bringing eth0 up via dhcp...............[ !! ]

some other PC's in local area can reach the internet but i don't know why my pc can not?? Additionally i can't ping the others too.
thank you

please post output of the following commands :
lspci
ifconfig eth0
route -n
cat /etc/resolv.conf