Okay,
here's the problem .. my http just went down and plesk is supposedly working on it. when we try to start apache, it says
"failed to restart Apache".

Are there any ideas as to why it would say that?

What does your apache log say?

yes, check the log. That should be your standard first point of attack when solving any problem.

tail /var/log/httpd-error.log

Did you do anything to vhost.conf file?