Hmm, when running it in the production environment instead of my test environment it works fine... I'll have to look into this. Both environments run on the same versions as well:
PowerCLI> Get-PowerCLIVersion
PowerCLI Version
VMware vSphere PowerCLI 5.1 Release 2 build 1012425
PowerCLI> $psversiontable
Name Value
---- -----
PSVersion 3.0
WSManStackVersion 3.0
SerializationVersion 1.1.0.1
CLRVersion 4.0.30319.18034
BuildVersion 6.2.9200.16481
PSCompatibleVersions {1.0, 2.0, 3.0}
PSRemotingProtocolVersion 2.2