Wandering through some of the old posts today, I noticed that external links in posts were coming up blank with "You must be registered to view this link"...

I'm assuming this is a glitch, right?

You should tell me what posts are (links)

Usually a non registerd user can't see links on the site (this is mainly because spammers use to post links and bots are not registered so it's useless to spam on PF )

I think that you shoud delete the cookies and try again, or give me the link so that I can check, it can be a permissions problem, but without clues I can do little