When installing SQL 2008 64 bit in an Active-Active 2 node cluster on Windows 2008, SQL Agent starts up with the following error on one node:
 Subsystem 'PowerShell' could not be loaded (reason: The system cannot find the path specified)
The follow query:
select * from msdb.dbo.syssubsystems where subsystem = 'Powershell'
returns the agent_exe as "C:\Program Files (x86)\Microsoft SQL Server\100\Tools\Binn\SQLPS.exe" when run from either instance.
The tools directory exists on one node, but not on the other node. This has happened to me on 2 different clusters. It make powershell unusable in SQL Agent for either instance when they are running on the "bad" node.