I have this same issue. I've been troubleshooting to try to figure out if it's the FFUC or the macbook pro (mid 2010) I really want to use ine live as well.

Not sure if that post was only aimed at the OP but as for me I'm using a mid 2010 Macbook pro with UC and I can't use it live yet. I wish I had more tools to diagnose the problem. I don't need 'Magic' but I just need to be stable with 128 sample buffer. A macbook pro i7 should easily be able to handle this task. My CPU is always 35% or lower. I'm not sure if it's a background process since it happens rarely but enough to keep me from playing live. It's a very strange sounding audio glitch. This is not the normal pop or click people speak of with buffer underuns.

I get amazing recording performance with Reaper but trying to use Mainstage or Bidule for live performance is when I get these glitches.

Again, I would love to hear of some tools or methods to help me diagnose this problem but  so far all I've heard is to search for IOAudioStream in the Console after it happens. I've done that located these message but I don't have a computer science degree so I don't know where to go from there:)

I completely understand the OP's frustration because the main reason I bought both of these was to perform live. These were two very major purchases for me (Macbook pro i7 17" + FFUC) yet I seem like I'm in the same situation as when I used an old macbook white and an motu ultralite. I made the false assumption that if I throw 3500 american dollars at my live performance issue my dreams would come true and all my problems would go away. Now after spending that kind of cash I realize I made the wrong decision. I will have to continue to  spend my time troubleshooting instead of making music and all the while working my tail off to continue to make my payments on this (at least to me) extremely expensive gear that doesn't accomplish the task I purchased it for.

You live and you learn.

You advertise the UC as 'The low latency product' I was able to run at 128k on the same machine with a Duet with ease and even at 64k which worked also but less reliably. With the over heads of firewire exactly how is your product ANY better for latency? All the talk of how you have bypassed the usb protocol by writing your own and so one but at the end of the day is it just advertising hype? Its very much starting to feel that way.

So If I go out and buy brand new MBP tomorrow and Im still getting the same problem is RME going to pay for my new machine?

or even fix/replace the product they sold me.........

I know what audio sounds like when a computer cant cope with the latency and this problem ISNT it, the UC plays at 64k with no pops clicks or signs of stress which is why I bought it when I tested it in store and 'upgraded' from the Duet but every so often it quite literally SHITS its self. All I upgraded was my mastercard debt.

Funny, your advertising of the UC suggests as much. I broke a cardinal rule buying th UC which is NEVER buy usb interfaces, I feel like such a stupid consumer victim of advertising.

Well when the UC was released the i5/i7 had been out only 1 month meaning rme would have been developing the UC on the core 2 platform, Core 2 could hardly of been considered an old/surpassed architecture at the time, yes mine is older but the technology is still a core 2. My cpu is never above 40% so I am not stressing my system by any means, I dont want to sound like a whiney little bitch but Ive been down the 'buy the latest/most expensive' path before and it almost never solved my problems and nearly always created new ones.

With in days of posting this another user WHO ALSO HAS A NEW MACHINE says he has similar issues so this just strengthens my argument against throwing away more good money......

So basically your telling me that your 'low latency' product cant achieve any lower latency than the countless other (and far cheaper) firewire products on the market?

this IS effectively what you are saying if your stating my computer is to old when an old school DUET was able to achieve much the same.

my reply is 'NOT EVEN CLOSE TO A GOOD ENOUGH RESPONSE'

whats really sad is that a part of me wants you to be right and believe that buying a new MBP will solve everything, that would be easier than the FULL YEAR OF FRUSTRATION Ive had to endure with the promise of just being able to make music with a laptop that RME and others advertise, but thats how you 'get' us isnt it and keep the cycle of consumers buying 'the next' thing............makes my blood boil.

If your it's computer, then Macbook pro are not the answer. My 2010 MBP i7 is not the answer and someone else posted they have distorted sound problems with a 2011 Macbook pro.

I'm curious then which PC notebooks have solid performance with the Fireface UC? No strange glitches or dropouts at 128 sample rate buffer with up to 40-50% CPU usage. This would be the ultimate. I have never experienced that yet.

Is there anyway for people with USB issues on the new MBP's to swap a UC for the firewire version?

On your MBP, maybe. But maybe not, considering it doesn't perform that much better with the Duet.

More likely IMHO.

Certainly not from RME. Nowhere do we claim that our sound card solve inefficient computers' inherent performance issues.

The UC allows the use of such low latencies. It's still the computer that has to complete all required chores (effects, virtual instruments) withing the specified latency time.
There are other potential causes of disturbance, of course, matters of individual system configuration - have you tried disabling Wireless Network? You could also search this forum and you will come up with lots of threads discussing Macbooks, maybe some will contain helpful information.

How does this imply that the UC can actually actively improve a computer's performance to enable it to perform at significantly lower latencies than before?

Regards
Daniel Fuchs
RME

I have this exact same issue. Not sure if you've already done this but Oblique Strategies told me to search for IOAudioStream in the Console application right after this happens to see if you have any errors and I did.

There has to be some way we can get to the bottom of this.