I just added the Broken Steel DLC and started off with a save game near the Jefferson Memorial door. AFter fighting off the enclave soliders and dealing with the Colonel, nothing happenes. No Dr. Li there or the lady Paladin. I m just stuck in the Rotunda.
I have finished the main quest earlier but what it this?? I tried various things to overcome this bu no fruit. Even tried with other's save games but the result was the same.
Help me in this please. As point look out is out I need to finish broken steel soon....Thank you

I initially had this trouble too, but it turned out I did not have the DLC installed correctly.

When you download from Games for Windows LIVE it will say 'Installed' but it is not to be believed, there is more to it - See my post You are not allowed to view links.
Register or Login for more information on how to correctly install it.

Good luck.