1.  On the actual Macs, right?  Yes wifi isn't even installed on these.  The Airport extreme is wireless as well as wired, though these machines are all wired.

2.  Internet Sharing in System Preferences are disabled.  If you mean something else, I'm not really sure.

Here's another strange element of the puzzle, the dropouts happen at very regular intervals - about every minute, which makes me think it it some kind of network issue.

What happens if you just connect the computers to each other without going through the hub?

Same problem

So this is only happening to 2 people then?  Is anyone else using an Apple Airport Extreme - are you having any issues?  Does a WIN slave work better than a Mac Pro (I can run Win on my second Mac if VSL would work better).

im using a DLINK Gigabit ethernet switch with no problem.Im picking its the settings within the airport extreme basestation.You don't want it to be connected to the internet.I couldn't get my two macs to work with VEPro without the Gigabit ethernet switch.I also have the network settings in my mac set to manual.

Daniel,

Run, don't walk, and get a dedicated gigabit switch. Using a wireless router as a switch may or may not get you your desired results. I have read about port throughput and some routers have less than rated throughput -- a switch will simply connect your devices at the speed they need. Then connect the switch to your router, but make sure the router has a gigabit LAN port.

Check this site out for router benchmarks:

http://www.smallnetbuilder.com/index.php?option=com_chart&Itemid=167&chart=121

Yep, that fixed it.  Now the only issue I have is when a track is selected in the Arrange Window, my 8th core peaks...

I had the same problems (peaking core, pops, etc.) although the computers are connected physically (no hub at all).  This fixed it:

Go to Logic's preferences > Audio > Devices and increase the I/O buffer size. 

Also, I had two Firewire audio interfaces daisy-chained and aggregated as one unit within OSX.  When I de-coupled them and plugged both directly into the Mac, the performance was even better.  (So, remember that Firewire is another "network" type that could interfere with performance.  Maybe external Firewire disks could even play a role?)

Oh, restart Logic Pro after changing those settings, too.

Hope that helps.

- Paul

Thanks - I'm already at 256 - any more than that and the latency is too much for me to stand.  I've noticed when I am listening back, if I choose an empty audio track to select instead of a MIDI track, the problem goes away - something I can live with.  Would more RAM help? 

@daniel.lee said:

Flue Oboe Clarinet BassonThanks - I'm already at 256 - any more than that and the latency is too much for me to stand.  I've noticed when I am listening back, if I choose an empty audio track to select instead of a MIDI track, the problem goes away - something I can live with.  Would more RAM help? 

I think you need to investigate how Logic works. Look up playback buffer and live mode (I think that's what they're called).

DG