I'm experiencing a weird dropout pattern that I can't seem to troubleshoot, or even understand how it is happening the way it is. I'll open a project and press play. At a certain point in the track, I'll get a dropout. The now line (if that's what it's called, I'm sure it isn't ...) stays where it is, and if I try to press play again, playback won't even start. If I back the now line up by a measure or two, playback starts until it hits that same spot, or within +/- 0.5 seconds of that same spot, and then the dropout happens again. If I move the now line forward a few measures, playback won't happen but if I move it much later into the track, it will play. When playback is started from after the "dropout dead zone", it will continue until it hits another such dead zone, where the same behavior occurs.
 
The part that is really stumping me is that there seems to be NO reason whatsoever why the dropouts are occurring where they are. It isn't anywhere near a new synth responding to MIDI for the first time, or several more tracks of audio hitting the processor at once, or one track of audio with 8 plugins on it, or anything crazy. It even seems to happen in almost the same spots when I close and reload the track.
 
I've mostly had this happen on one project, but is has occurred on at least two others, so the problem is not with the project file as I originally thought. Things I've tried that didn't work:
 
Closing/reopening the project
Turning off all FX globally
Unloading all soft synths and samplers
Archiving groups of audio tracks (this initially worked once, until I reloaded the project, Archived the same tracks and got the drop outs again)
Saving the project as a bundle and reopening said bundle
Applying Manchester Update 1
 
I THINK this started after the original Manchester update, but I'm honestly not sure. So yeah, lil help?

You haven't mentioned in your "try" list increasing Asio audio buffers in Sonar preferences ?

 
Any chance you have automation on the track/bus cutting out the sound for certain periods of time ?

noynekker - No I hadn't. I'd been running everything fine at those same settings for a while, but I went ahead and messed with it for science. Increasing the buffer on my interface to 20ms (the maximum it allows) made no difference. I changed the I/O buffer size for playback in Sonar preferences and things started to get weird. I had it set at 256 buffers, and changing it to either 64 or 1024 buffers both caused playback to start with a long delay and produce no sound. Changing it to 128 gave the same results as the 256 setting. Nothing solved, but good idea.
Paul P - No automation in the project

I have had this oddity on a few projects, my work around was this.
 
At the exact point where the project locks up join the clips together on their respective tracks.
 
Hope this work around works for you.

You could have a corrupt wave file. Try archiving each track one at a time to isolate the broken one. If you do find a corrupt clip, you may be able to salvage it by bouncing the track to itself. If that doesn't work, try a slip-edit to eliminate the broken part. If that doesn't work, split the clip before and after the break point and mute the broken part. If that doesn't work, that part of the track is toast.

I was going to say the same thing.. Do you have back up copies of the project? 

Thanks guys
 
I did some playing around with this and got some interesting results, but nothing that actually GOT me anywhere unfortunately. I opened the project in question and let it play until it hit the first dropout. There were only 3 tracks with audio going at that moment, and none right at a clip juncture point, but I tried joining the 2 clips closest to the drop point on each track anyway. One of the tracks kept giving me an error when I tried to bounce the clips, so I deleted each one in turn, and after deleting the second one the project played fine. I noticed that when I truncated the front end of the clip by however much, the dropout point moved within the project to a couple seconds before the start of that clip. I undid the bounces and opened a backup copy of the song, copied the offending clip, and re-opened the problem project to paste it in. Just for the hell of it, I tried playing the project back again and it played right through the clip (the one that had been in the project - I had not pasted the backup copy into the project yet). This time, playback stopped just before another clip in a different track.
 
I do have backup copies of everything, so my next step might be making a new project and importing all the audio files again. I'm currently mixing an album while cleaning up the programming on it, and I've found it easier to import all the audio from each song into a new project where all the tracks and busses have certain plugin chains already set to go as opposed to saving each and every chain and then loading them up one by one in the original project (there are enough similar sounds from song to song to make this approach economical). Based on what I found when I was working on it earlier today, it seems as if Sonar is having trouble loading all the audio in the song simultaneously, so it randomly de-prioritizes a few pieces of audio when loading. I've successfully opened projects with all the same audio clips in them dozens of times before this though, and my RAM meter isn't saying it's anywhere near full (probably about 30% for this project).
 
I'm starting to think it's something in Manchester, does anyone know how to roll back to Lexington?

Right-click the SONAR Platinum line in the Command Center. Rollback is a option on the context menu. The available versions are listed in the rollback submenu.

Thanks scook, unfortunately rolling back didn't work.
 
I noticed something new this time: One of the clips in the project (right at the start of it in fact) all of a sudden went visually blank. By that I mean the waveform disappeared, the little "record #" tag disappeared, and the clip turned grey. There was a dropout when it happened, but when I pressed play again, the track continued. The sound of that clip after the dropout was SEVERELY garbled and distorted. The best way I can think to describe it is it sounded like a bit crusher had been used on it to take the bit depth down from 24 to about 3-4, but then it also sounded a bit more "chaotic" than that. I reloaded the project and playback would take a couple seconds to start, followed by no sound at all.
 
It's almost starting to sound like a hardware issue or something, like my RAM is going bad.