I think what some other posts were trying to say which may need clarification is that in PHP 4.2.3, ftp_connect("myhost.com") was failing most of the time, except it would work like every few minutes.
The fix is that ftp_connect seems to have a bug resolving addresses. If you do:
$hostip = gethostbyname($host);
$conn_id = ftp_connect($hostip);
It seems to solve the problem.
(Other users referred to an ftpbuf() error... not sure what that is, but this should fix it.)