We have had a few clients run into problem when they are attempting to integrate:
DropDown Login Skin object
Dynamic Login Module (a feature that DropDown Login can support if you want a custom template etc…)
Facebook Connect – The Facebook Connect feature within Dynamic Login.
We have had a few clients that have recently been integrating Dynamic Login with Facebook, Twitter, and Linked In and these clients have faced a few issues getting everything to work… This can be difficult to debug because a lot of the functionality is happening behind the scenes. Review this blog post if you are integrating Dynamic Login with either Facebook, Twitter, or LinkedIn and are running into any problems.