UBB.threads PHP Forum Software Community Forums Resources and Customizing How Do I? Have to log in twice--why?

I have a feeling there’s an answer to this query on this board somewhere, can’t find it though. Ever since upgrading to version 7 neither I nor my users can login on the first try; i.e., it takes two login attempts before login is successful. Anyone know why this is and/or how to fix it?

Thanks!