No. If the script finds no domainkey for a domain it sends it unsigned. Several of us use qmail in a cluster environment without problems.
Good chance you have a corrupted queue, and since qmail-remote's job is to send it, it is hanging. Goto KloxoMR panel and look at mail queue, report it here. Watch for a message or messages not leaving the queue.
As we can see, the problem IS NOT with signing, since you had him rename a file, which is never a solution. Reinstall your toaster packages.
Did this problem always exist on this server or is it recent?
SSH:
yum reinstall *-toaster
SSH:
vim /var/qmail/control/softlimit
If 64 bit file should be
/usr/bin/softlimit -m 72000000
If 32 bit change above number to 1800000.
Run fixdomainkeys in case a domain key is corrupted, but unlikely
SSH:
sh /script/fixdomainkeys
Do as Mustafa also said and reduce Max smtp to 25 - 50 in KloxoMR panel under mail settings.
Do this on the server with problems, and all at once, no need try each solution, they are all part of one solution.