I've been running VMware Server on the SilverShuttle for a while now (140 days and counting!). The little machine is generally running very well with its two VMs - Solaris Nevada and CentOS, but occasionally the machine stutters very badly and the load average within the virtual machines shoot up from the 0.1 they usually are to about 40.0!
Unfortunately, running top and prstat did little to suggest any reason, and the host operating system (SUSE 10.1) didn't seem to be having any problems of its own apart from the VMware processes which were now taking a lot more CPU.
Cutting to the conclusion, after a period of investigating what might be the cause, I turned off the powersaved daemon on the host operating system. Since then, performance has been rosy. I'm guessing the powersaving was kicking it, misreporting the CPU speed to the VMs which were then choking (but it's just a theory).
All is now well.