Cookie problem

I'm experiencing all kinds of problems with, what we suppose is the cookie setting. This is the code: if (isset($authentication)) { setcookie("status", $status, time()+600); setcookie("user", $user, time()+600); setcookie("group", $group, time()+600); setcookie("authentication", $authentication, time()+600); setcookie("laston", $laston, time()+600); } else { setcookie("status", "Logged In", time()+600); setcookie("user", $txtUsername, time()+600); setcookie("group", $row[4], time()+600); setcookie("authentication", "YES", time()+600); setcookie("laston", $row[6], time()+600); } (I have not coded this). What seems to happen is that - with alarming regularity - people are getting logged off when choosing item from a menu. Either they are thrown out into the log on-screen or (as has happened to me recently) the app simply states I'm not logged on even if I am in the middle of using it (and must have logged on). I'm not at all familiar with cookies (yet) but suspect that the timing of the critters could be a culprit. IS this correct? How do I solve the problem? M.