WPMU Error Log Monitoring

I have a two part question here... One is in regards to a problem that I'm having and the other one is a general question.

1. I can't seem to figure out why I'm getting the following error:

arning: file_get_contents(/home/netprof2/public_html/wp-content/plugins/whmcs-wordpress-integration/cache/5e24e98300eacaa82315b8e92e667d82.txt): failed to open stream: No such file or directory in /home/netprof2/public_html/wp-content/plugins/whmcs-wordpress-integration/includes/class-whmcs-wordpress-integration.php on line 376

I checked my integration page and it shows that error at the top... I disabled the plugins that were active for that site and just activated the integration plugin and the error showed up... so it doesn't seem to be a plugin issue at the site level. Any idea what it might be?

2. Are there any good plugins out there that will actually monitor your wordpress network for errors? Basically what I'm looking for is something to alert you when one of the sites on your network produce an error that way you won't have to worry about sifting through error logs or waiting until one of your clients bring it to your attention...