Thanks for your reply! I hope that fix will work for me, as well. I've lost several e-mails in full or part due to the problem even though I never changed the setting from the default 60!
I guess I won't be checking that e-mail on a public computer, is all! Or I'll have to remember to delete the cookie - that will make it secure again, correct? I don't normally use public computers, anyway.
Speaking of the cookie - I couldn't find it in my Cookies folder while I was logged in the other day. It was not under my site's name. Does it use a certain RoundCube cookie name instead?