more on cookies..

I'm renewing an older PHP project that made use of PHPlib for sessions and don't want to rewrite the project from scratch to use PHP4 sessions. The current sessions seem a bit buggy. After setting cookies to last 14 hours, and verifying that the cookies are being set for 14 hours, they are expiring somewhere between 1 and 15 minutes after being set. Any idea what might be wrong? I didn't write the original codebase for this project so it's possible something odd might be happening someplace like the cookie being deleted and reset but I'd like to have suggestions before digging through 30,000+ lines of code for something that might note exist. ;>