When creating a VM with a custom compute offering, CloudPlatform allows the input of double-byte numbers. The VM will be created but listVirtualMachines will subsequently fail with an exception. The problem seems to be with the value of detail_value for the associated entry in the user_vm_view table. If you manually change it to a regular number the issue is resolved. Double-byte numbers should either be considered invalid for custom offerings and rejected, or listVMs should work when they are used for a VM.