Hmmmm... yesterday, this page was page rank 4, today... no page rank. Go figure!
Page Rank is an indication of a site's importance within a category of search terms. It goes on a scale from 0 to 10. Some categories, don't have PR 10 and their highest rank may be much lower.
One factor that affects your google ranking is how many highly ranked pages link to you. You won't be hurt by low ranked pages linking to you, but you may not be helped.
Where your page ranking can be hurt is if you link out to pages not in your category, and it seems that the higher ranked your wrong-category outbound links are, the more you are hurt.
As with any other "advice" about search engines, what's true today may be wrong tomorrow. Your best strategy is still to have good content.