Well, this is definitely a server-side thing, since the page numbers and so on are all set up on that end. So switching browsers, clearing cache, and the usual client-side remedies should have no effect on whatever is causing the issue. Unfortunately, the server logs don't appear to show anything unusual for the time period around when you posted, so... I'm not totally sure what could have caused this.
One possibility, albeit remote, is that the SQL server NGA uses was upgraded recently (this caused some brief downtime, sorry everybody). Perhaps this is a transient, residual effect? The delay since the upgrade makes this much less likely, but I'm not sure what else it could be.
If it shows up again, please do let us know. And always feel free to PM me about technical issues too!