Syntax error executing Maintenance Plan job

I'm running SQL 2005 SP2 on a cluster.  I have a maintenance plan that backs up databases.  When I execute the job associated with the plan, I get the following error:

Unable to start execution of step 1 (reason: line(1): Syntax error).  The step failed.

This only occurs when node 1 is active.  When node 2 is active, the job runs with no problem.

I edited the job, and it references the package

Maintenance Plans\PlanName

If I add a leading "\" to the package path so that is reads

\Maintenance Plans\PlanName

then the job runs successfully on both nodes.  So the question is why would this fail on one node and not the other?  I know there are SSIS issues when applying SP2 on a cluster, so we applied it on each node.  SSIS is running version 9.0.3042 on each node.

Thanks,

Tom