I kept getting a shipping error, and even though all of the other posts on this were helpful, they did not work in my situation. I upgraded to VM 1.1 today and broke my USPS module. I did everything suggested with no solution.
Finally, I came across this post: New registered users will not need to enter a password in the password field, if you have one, great, I believe you don't need it.
I tried for the heck of it entering my password, and BAM it worked! So even though just about every post on here says you don't need a password... you might need it
Hope this helps someone.