Stay calm. Get yourself a cup of tea, coffee, soda, etc., and have a rest. Once your mind is clear, try the suggestions mentioned below. Setting up Linux IP Masquerading is NOT hard but there are several concepts that will be new to you.
Again, go through all the steps in Chapter 5. 99% of all first-time Masquerade users who have problems haven't looked here.
Check the IP Masquerade Mailing List Archives, most likely your questions or problems are a common one and can be found in a simple Archive search.
Check out the TrinityOS document. It covers IP Masquerading for both the 2.0.x and 2.2.x kernels and MANY other topics including PPPd, DialD, DHCP, DNS, Sendmail, etc.
Make sure that you aren't running ROUTED or GATED. To verify, run "ps aux | grep -e routed -e gated"
Post your question to the IP Masquerade Mailing List (see next the FAQ section for details). Please only use this if you cannot find the answer from the IP Masquerading Archive. Be sure to include all the information requested in Chapter 5 in your email!!
Post your question to a related Linux NNTP newsgroup.
Check your configurations again :-)