If you have an HPC Pack 2008 R2-based cluster that you have not yet upgraded to SP1 - Why?
Were you unaware that a service pack had been released, are you still evaluating the service pack on a test cluster, do you have a policy of not applying updates unless you are seeing problems, etc...
http://www.microsoft.com/downloads/en/details.aspx?FamilyID=A78520F1-DE82-4442-B273-2FF7327B9140