This came up not too long ago. So do a "search" on this site. Type in Separation Anxiety probs and a couple of posts should come up dated June 2006. Hopefully they will give you some ideas.
I also have more info written by a knowledgeable lady that has gone through this with 2 dogs and of course is still working on it but they are doing well. I will send this to you via e-mail. A couple of other suggestions would be to sign up for an obedience class. Also contact a certified pet behaviorist. You really need help to correct this problem. You might be unknowingly enforcing this behavior instead of correcting it.
Let me know if you are unable to make the search work.