Empty Post Variables

I am running PHP / mySQL on Netware 6.5. I have an app that takes a data from an HTML form and inserts the data into a database. Unpredictably, however, the variables that should contain the post data are sometimes empty. Register Globals is set to on, and I can't access the data either through the $_REQUEST['VARIABLENAME'] or the $variablename format. Hitting the refresh button a couple of times seems to get the data into the variables, and other times it goes through on the first try. I can't be 100% sure, but it looks like other global variables like remote_user seem to get to the script without a problem when the post variables don't. Any help would be greatly appreciated. Trevor Shaw