It sounds as if your dialing properties could have changed.  Let's go check them.

1. Go to the desktop.
2. Double click on the "My Computer" icon.
3. Double click on dial-networking.
4. There should be 2 icons in here ("Make New Connection" and "BSC-Net").
5. Right Click on the BSC-Net Connection and come down to properties and left click.
6. You should now be looking at a screen that looks something like the one below.
   
7. The telephone number should be the one that your computer dials to connect to BSC-Net.
8. If this is ok, click on the "Server Types" Tab.
9. You should now be looking at a screen that looks like the one below.  Check your setting against the picture below.
   
10. .Next, we should click on the "TCP/IP Settings".  Just click on the "TCP/IP Settings Button" in the lower right hand corner of your "Server Types" Page.
11. .You should then have a screen like the one below.
12. .Check your settings against the screen below.
    
13. .After making the changes, Click "OK" all the way back out and go try to hook up to the internet again.