QOS Alerts And Sites Running Slow On Occasion

My sites have been receiving a little more traffic these days (but not too much) and it seems my vps is slowing and at times vbulletin/wordpress page doesn't loads or loads a bit sluggishly (refreshing the page gets rids of not loading issue but not sluggishness).

So I logged into Virtozzo and saw the following QOS alerts:

Jul 05, 2008 11:38:25 AM Green zoneGreen zone kmemsize
Jul 05, 2008 11:38:25 AM Green zoneGreen zone tcpsndbuf
Jul 05, 2008 11:34:54 AM Green zoneGreen zone privvmpages
Jul 05, 2008 11:33:54 AM Yellow zoneYellow zone privvmpages
Jul 05, 2008 11:33:15 AM Black zoneBlack zone kmemsize
Jul 05, 2008 11:33:15 AM Black zoneBlack zone tcpsndbuf
Jul 05, 2008 11:28:05 AM Black zoneBlack zone kmemsize
Jul 05, 2008 11:28:05 AM Black zoneBlack zone tcpsndbuf
Jul 05, 2008 11:27:55 AM Red zoneRed zone tcpsndbuf
Jul 05, 2008 11:22:55 AM Black zoneBlack zone kmemsize
Jul 05, 2008 11:22:54 AM Black zoneBlack zone tcpsndbuf
Jul 05, 2008 11:17:54 AM Black zoneBlack zone kmemsize
Jul 05, 2008 11:17:45 AM Black zoneBlack zone tcpsndbuf
Jul 03, 2008 05:31:29 PM Green zoneGreen zone othersockbuf
Jul 03, 2008 05:26:19 PM Black zoneBlack zone othersockbuf

I have previously seen tcpsndbuf going into yellow and even black zone (but only once in a blue moon) however never saw kemsize going into black zone.

These are the limits my host has set:
IDCurrent UseSoft LimitHard LimitUnits
tcpsndbuf301,8602,580,4804,055,040bytes
kmemsize9,135,28929,614,08030,474,240bytes
othersockbuf17,8881,689,1203,145,728bytes

My Cpanel VPS has around 384MB of dedicated ram and around 896Mb of burst Ram. At any given time, there is at least 150Mb of free dedicated RAM. So based on this, are these values correct or they need to be changed or do I need to look for something else which might be causing this problem?

I don't run Spamassassin