setcookie() woes

Hi all, I have a login script that works on one of my machines but not another, and I've determined the problem has to do with setcookie(). One machine is using IE 5.50 and another is using 5.00, and I assume therein lies the problem. I've tried to plow through the dozens (hundreds?) of followups on the manual page for setcookie(). Most of the interesting ones seem to involve using header("SetCookie . . .") instead of the setcookie() function. I tried a few, including the pass-every-parameter-to-setcookie-even-if-you're-not-really-using-them workaround, to no avail. Is this a well known problem, with a well known solution? Thanks, Chris