Not staying logged in?

[hhmoore]

For about the past week or so, I've been finding myself being (seemingly) randomly logged off. Sometimes it's when I've been offline for a few hours, sometimes it happens when I've been active - during a page change. Most recently, it seems to be happening at least once daily. It's been twice already today.
Yes, I click the Stay Logged In box when logging in.

Any ideas?

**Edited to add - make that three, I had to log in again to post this thread...and I had just logged in prior to starting it.