Imap session lock

I had a problem using php on Win98 to read an emailbox on pop3. My script runs okay in the first time. But the second time onwards it returns "Fatal error: Your mailbox is locked by another POP3 session -- please wait a few (up to 10) minutes and try again." even I using IMAP_close after the first time using IMAP_open to open a stream. Is it related with email server setup or something we can do about it? your advise are appreciated. thanks -- ********************************************** Dr. Gangmin (Gary) Li * Research Fellow Knowledge Media Institute (KMi) The Open University, Milton Keynes, MK7 6AA Tel: +44 1908 858519 * Fax: +44 1908 653169 http://kmi.open.ac.uk **********************************************