For some reason, Ubuntu 10.04 thinks I do not have a connection to the internet, when yesterday I did. I have Windows XP installed via dual OS boot, and the internet connection works perfectly.
What's going on?
You might try running these commands on Ubuntu to see if they clear up the problem.
This command should reset the whole networking system on your system and automatically renew your IP Address and fetch DNS servers and the such from your router.
These two commands are helpful if you ever run into problems with your ethernet connection. The drop and restart your wired connection.
was it a clean install you did yesterday? if so perhaps the kernel has updated during post-install updates.if so you might have to compile your drivers for your network interface against the new kernel. check akseli's answer to see if you have in interface functioning, if you dont you should download latest tarball module for your network card, ./configure make && make install