[Zope] Is somebody else having problems with the speed of their Zope-site...?

Hi there... We, HeadNet, are having an frustrating problem... Our server (linux, apache, zope 2.5) is working fine, except when we are entering the site.... (http://www.headnet.dk) sometimes it reacts really quickly, and sometimes it is slow (up to 20-30 seconds!) One thing "helps": If we have the main-server restartet (there is approxiamtely 15-20 InstanceHomes, some of them have the same problem but not all...) it helps a bit... One of the strange things is that the speed of entering the site is going up and down... we actually have no idea, why or what to do about it... Have you had / are you having the same problem... we would very much like to hear from you... / Stoons : HeadNet :