If you have a print server failover cluster on Windows Server 2008 R2, Microsoft recommends you install this update immediately.

http://support.microsoft.com/kb/976571

Read this great Blog post from Symon Perriman, Program Manager for Microsoft’s Clustering and High Availability Team for more details.

http://blogs.msdn.com/clustering/archive/2010/01/22/9951795.aspx