If a device is already claimed by an application, attempts to claim that device by applications running from different user accounts fail. POS for .NET returns an Argument exception instead of a POS exception. Once a user account receives this failure, subsequent attempts by that user account to claim the device fail, even after the device is released.
This failure does not occur for two applications running from the same user account. Access to the global event is denied only for different accounts.
for other considerations.