We've had reports of a bug with clusrun, specifically that environment variables set using the /env flag to clusrun may or may not get propagated to compute nodes when the clusrun job is run. For example, doing "clusrun /env:test=ItWorked set" would result in some nodes reporting the test variable as set and others reporting it as not existing.
As it turns out, this is due to a race condition in the clusrun submission code. We hope to have it fixed in the upcoming Service Pack to the HPC Pack. In the meantime, you can work around this issue by replacing the above command with the following one:
clusrun set test=ItWorked^&^& cmd /V:on /C set test