I was experiencing an issue with LastPass on three separate sets of wordpress sites, and finally tracked it down to a conflict with jetpack.
Symptom: Although logged in to the wordpress site, the lastpass popup keeps coming up at the top of tha page, saying it's filled in your login information for you. The popup is only supposed to show when you are not actually logged in to a site.
I thought it was a bug in lastpass until I discovered it only happens when jetpack is activated. I've reported the issue to them as well.
I need jetpack features and I need lastpass, so I hope this gets cleared up quickly. I'm available for testing a patch if someone comes up with a solution.