Alcatel Speedtouch gives a lot of people trouble, and no one has found a complete solution for it yet. I'm almost sure there is one though.

Edit: What model specifically?

Edit #2: I found this site which could be the final answer to the Alcatel Speedtouch problem many have been having. Either that or the answer is bridging (which is more complicated but can be done). If you follow the link and follow what it says, I highly suggest running another firewall in the background.