Problems reading member's posts

I've been trying to read a member's posts and it wouldn't let me - I went to the member's profile and clicked on "find all posts by ...", and this worked fine just a few hours ago - then I wanted to get back into that member's posts in order to reply to some of them and each time I tried to do so, a message came up saying "Sorry - no matches. Please try different terms". I can access all other members' posts without any problems.

The member concerned has not been online since I read their posts earlier so there has been no change to their account.

Anyone got any idea what's going on there?