I've been experiencing an issue installing the plugin on my windows 7 x64 Enterprise with Chrome 16.0.912.77 m.
When I click on Install Plugin and tick the box I have read and accepted the Service User Agreement it download the file npqbc.crx but I have a windows popup that says:
Package is invalid. Details: 'Could not create directory for unzipping C:\Users\jeff\AppData\Local\Google\Chrome\UserData\Temp\scopped_dir25867\CRX_INSTALL'.
I've reviewed the permissions on these directories and they are writable.