PokerTracker

Was in session and this popped up? Never happened before. Anyone have any ideas?

Thanks in advance.
Luke

It means exactly what it says - there's a limit on the number of observed hands (that is hands you weren't playing in) that can be imported into PT4 in a given session.

Given that you say you got it during a session it likely means you don't have PokerStars set to save your hands properly - you can set that up as explained in our PokerStars Configuration Guide.