This post discuss an issue with Windows Server 2003 that caused the Certificate Template Manager to hang. If you try to open the Certificate Template Manager (certtmpl.msc) in the affected forest, it will not open…on any computer in that forest. If you look at task manager after attempting to open certtmpl.msc you will see mmc.exe consuming 100% of the CPU (50% if you’ve got 2, 25% if you have 4, etc.) regardless of how long you let it run. The only way to stop it is to end the process.