I've experienced much weirdness on poorly configured virtual windows platforms. Our client had outsourced the installation and management of virtual platforms to a well known Outsourcing firm. The application in question was not written in Perl. When running on a normal windows server the application behaved reasonably, once migrated to a virtual platform it performance was unacceptable. At this point the resource utilisation was minimal. After much fruitless investigation on our part our client arranged for another virtual server (built in house, on the same blade platform). We couldn't replicate the problem on the new instance. The company responsible for the virtual servers couldn't track down the problem. Shortly after our client terminated their contract their, apparently because they didn't seem to have any idea what they were doing.