With 3 posts, it ain't likely you've overlooked a message.
I was going to point out that if he's got more than one page of PMs in his first day of being a member, he's one popular dude!
It seems to be an issue with most, if not all, of the members who have joined recently. Many new members have posted the same issue but haven't seen any of them post what the fix is, if there is one.
ETA- several have tried clearing cookies to no avail.