Remote registry key export/save/import/restore...

I need to export registry keys from a remote computer for import into other remote machines (copy) using PowerShell V3.0.

When I use REG QUERY to view the registry keys thus:

    reg query \\[computername]\HKLM\[subkey] /s | Out-File -append .\export.log

all subkeys are recursively output to export.log as expected.

However, when using REG SAVE to actually save a copy of the registry (in order to use REG RESTORE to import keys into target computers):

    reg save \\[computername]\HKLM\[subkey] .\export.hiv

I am encountering the following error: "ERROR: The system was unable to find the specified registry key or value."

What's going on? Why can the REG QUERY find the specified keys/subkeys but not the REG SAVE?

The same issue presents when calling these commands from a Command Prompt..

Is it possible to export/import/save/restore remote registry keys using PowerShell? Is there a straightforward way to do this?