If you are using CentOS 5 , Oracle Enterprise 5 or Red Hat Enterprise 5 as a VMware host or guest you can edit /etc/yum.conf and add a line
this should prevent yum updating your kernel and thus breaking vmware services modules in vmware server and vmware services modules in vmware guest tools
xVM is a free, open source virtualization platform, which was unveiled at Oracle Open World, alongside our management platform, xVM Ops Center.
xVM will virtualize Windoz, Linux or Solaris, on either Dell, HP, IBM or Sun hardware.
xVM is based on the work of the Xen community. In a running system, Xen fits between the hardware and the operating system.