backup process hangs

I'm having a bit of trouble with the backup function. I'm backing up to a remote FTP server and everything seems to be fine, but the backup.cgi script hangs on one of the servers without completing the other servers, so the backup is incomplete. The only server that has this problem is the largest (~200MB). Is there some log I can check to troubleshoot why this is timing out without completing? What's also troubling is that no email is sent, because the backup never actually fails, it just hangs and this leaves several running backup.cgi processes which eventually start eating up a lot of resources.