I have noticed the PR of most of my Squidoo lenses drop from pr1/2 to unclassified in the last pr update. Is this because I haven't been actively contributing to Squidoo recently with forums, comments, ratings etc? (Due to time constraints, I have mainly been doing article marketing and have let existing lenses stand.) I know that Hubpages drop your hubscore if you stop joining in - does Squidoo drop your "Squidoo score" - ie the link juice it passes to your lens - if you stop joining in?
No there is no rules published by Squidoo as such. You need to build some links for it to get out of NA rank. Also check if it is been deindexed or not.
Sorry, what is your question exactly? First you talk about PageRank, which is a calculation of the links juice to your squidoo lenses, and then you talk about your squidoo score, which (as far as I remember) is like the alexa ranking based on the number of visitors.