LateArrival
Sounds like you might have inadvertently changed a setting somewhere. If as you say the computer was working fine a day or two ago, then I suggest you try a system restore.
If you are using XP, click on:
Start > All Programs > Accessories > System Tools > System Restore, then select "Restore My Computer to an Earlier Time", then Click on "Next"
Use the calendar to choose a date & time a little prior to when your computer last worked properly, then select "Next" and it will ask you to confirm the restore point selection.
Click on "Next" and watch it do it's thing. As part of the process it will re-boot your computer, and when finished it will tell you if the restore process was successful or not.
If successful, after it has booted up, try the internet again.
Let us know what happened. If not successful there are one or two other things we can try.
Good Luck.......LC