Problem with connecting with Samsung device (Galaxy Tab S)

I just purchased the new Samsung Galaxy tab S.

When I attach it via USB to my Mac Book Pro (OSX 10.8.4), Android file transfer starts automatically and everything is fine, it shows my tab S directory.

When I attach the same device via USB to my iMac (OSX 10.9), Android file transfer displays a message 'try to reconnect or restart your device' which I did many times, nothing happens.

What could be the difference between my two Macs ?

Thank you very much