Duplicate e-mails

I've a php script that gets e-mail addresses from a MySQL database and then sends the same e-mail message to about 100+ addressees. There are no duplicate addresses in the db. When I call the script the e-mails do get send but in duplicate and, instead of linking to a "Task Done" page, it shows "url not found". There is no duplication within the script and the url called is there in the same folder as the script. Is there a problem with php's mail function when it's used for multiple messages? Or is there a processing time limit that makes the script to be processed twice? Scripts are run using Apache under Unix. Thank you! Anthony F. Rodriguez (afrodriguez@att.net)