Hi all

My first post and big problem already. I am not shure if it is the RME UC issue but I am trying to narrow down the problem - maybe You could give me some hints. So here we go:

I have a four piece band - bas, guitar, vocal and electronic drums. The drummer plays VST drums (Addictive Drums) nested in Ableton to the click and sometimes (randomly) the whole set just starts to skip - like the whole clock just looses one beat. And I get CPU spikes in Ableton CPU meter.

I dont think its lack of power as the set is large but very light. Only few audio clips are playing at the same time and some midi clips plus few fx. I have also removed all the unnecessary stop buttons from the set to save cpu. The sample buffer is quite large (256) so I doubt its the resources problem... I downloaded all the latest drivers for my mac and fireface - still no luck. The strange thing is it never happens immediately - when we start rehearsing its all good - it gets freaky after an hour or so. And it only happens sparingly.
Sometimes its all good even when a drummer plays trills and dense rhytmhs and sometimes its goes mad even on the simpliest stuff. Please, please help as I got some serious gigs approaching...

I am on a standard MacBook Pro (late 2011), latest Lion updated.
coupled with Fireface UC interface latest drivers and firmware.

Here is the whole configuration:

1) Drum VSTs (Addictive Drums) and Ableton drumracks controlled by Drumkat via RME UC Midi in. I use all the RME UC audio outs for different drumkit parts and click signal. Plus I use one RME UC audio in for a sporadicall use of Ableton vocoder.

2) Ableton Scenes controlled by Behringer FCB 1010 via RME midi in

3) External FX (TC Voice Live 2) controller by ableton clips (switching presets and automating parameters via RME midi out

4) Virus TI Desktop (connected only via RME MIDI - without USB mode) controlled by ableton clips (midi notes and automation CC's) via RME midi

5) CME USB keyboard connected to Mac (with an aid of active hub to prevent excessive USB power consumption from the computer) comtrolling midi tracks in ableton.