Problems using 2 MyBook World Edition IIs as time machines for 2 separate Macs on the same network


I previously used a macbook pro and two mybook WEIIs on one network.  One of the drives was hooked up to time machine and the other stored my music.  The system worked fine.

I recently purchased a mac mini.  However, when this is switched on, my macbook pro can no longer connect to the time machine share.  When the mac mini is switched off it can.  I have now changed the music drive to be the time machine backup for the mac mini.  For 2 days everything worked as it should with hourly back-ups.  However yesterday the same problem occurred with neither computer being able to locate their back-up drives whilst the other computer was switched on.  As soon as one or other of the computers was switched off the other could back-up.

What can be causing the interference?

I have checked the network - each machine and each drive has been automatically issued with a separate IP address.  Both computers can connect to the non-Time machine shares on both back-up drives without any problems.  Mac Mini is connected both by ethernet and wi-fi to router - neither configuration makes any difference to porblem.  The hard drives are called different names and can be identified from each other.

Equipment - macbook pro and mac mini (both on Lion), Netgear router WDR3800 and 2 Mybook World Edition IIs.

You may confirm if both My Book World are updated to the latest firmware.  You can try resetting them, and have both connected directly to the router, no to a computer.

So came back this afternoon and couldn’t access the drives at all.  They are visible on the router but not on either computer (previously just the time machine shares missing).  Have switched off laptop and rebooted both drives and now visible (including time machine shares) on mac mini.

Both are running latest software - 01.02.12 and both are connected to the router and not the PC.  Following reboot and with Macbook pro still switched off the mac mini has successfully backed up to time machine.