Random(?) blank pages when using sessions

I'm using non-cookie-based sessions for authentication on a page. The session is set like so, which works (these values, along with the SID, are always retrievable): $_SESSION['user'] = $_POST['UserName']; $_SESSION['time'] = time(); My problem is when I get to the protected site area, in which a header script calls session_start() at the top (first line). Seemingly randomly, while navigating links within this area, I get blank white pages. If I comment out the session_start() line, it doesn't happen. If I spit out the session variables in the resulting page, they are echoed, but that's it -- it's a blank white page otherwise. The apache error log is silent, and the access log is normal. No php errors are displayed or written to the log. Here's the real kicker -- if I refresh the page, it loads correctly. What is going on? Thank you, -- Matt Grimm Web Developer The Health TV Channel, Inc. (a non - profit organization) 3820 Lake Otis Parkway Anchorage, AK 99508 907.770.6200 ext. 686 907.336.6205 (fax) E-mail: mgrimm@healthtvchannel.org Web: www.healthtvchannel.org