I recently updated from Sonar X2 producer to Sonar X2a.  X2a has been mostly good except for one major problem when trying to export a mixdown as a stereo WAV file.
 
Under certain circumstances some of the tracks in the mixdown sound out of time in the exported file, even though when playing the project in sonar everything sounds perfectly in sync. 
 
So the problem only occurs when I export the whole project and listen to the exported file. The exported file sounds awful in terms of timing with some tracks appearing to lag behind others by quite a large margin. Sonar itself plays the mix totally in time and there are no glitches or problems associated with playback in Sonar. 
Not being able to export a mix is a fundamental thing which all DAWS should do faultlessly.  So rather than get mad I thought I'd find out what caused this, and find a work around, so this post details how this problem occurs and how to fix it. I've seen other posts on this forum concerning this issue with no answers from anyone.
 
 
The cause of the Problem:
From what I can tell, the timing problem during export occurs only when Sonar's arpeggiator is used on a midi or instrument track. If I don't use the arpeggiator the mix exports perfectly in time.
 
The work-around:
So how do you fix this? easy.. just freeze the arpeggiated midi or instrument track, so it's rendered as audio, and then export the mix.  After doing this, the mix sounds perfect.
 
 
So the only conclusion I can draw from this is, that there is a bug somewhere in Sonar which doesn't render the arpeggiated midi track correctly when exporting. The bug isn't there when playing the mix in sonar, so it's purely and export bug.
 
 
I tried playing with Synchronisation settings and a whole range of different parameters in Sonar to see if anything else affected this and the only thing which caused the problem was switching on the arpeggiator. It doesn't matter what sample rate you use or bit depth or how you export the file nothing else seems to cause this.
 
I hope this post is useful for anyone having the same problem as I did.

Is it just the arpeggiated track that's out of time or other synths in the project?

probably a bug, easy workaround.

a studio owner told me a long time ago to make all midi into audio before mixing, to "keep everything in the audio domain," so that's what i do, then archive the midi track. 

is this what most people do, or is it now common practice to mix midi and audio at mixtime?

i noticed a problem like this while mixing down a project that used Guitar Rig 4 for time-based glitchy fx on an audio track.  it sounded fine when i played the project file, but the rendered .wav sounded like crap because all the timing was off.  turns out it was due to the fact that the audio file was mono, and Guitar Rig didn't like that.  once i converted the track to stereo, the rendered time-based fx were right on! now i realize that this here is probably not as related to your problem as a comment on this thread should be, but it is an interesting little factoid regarding time-based vst

I have noticed similar issues with MIDI, and dlion16's suggestion is also what I do. I mix-down tracks prior to the final mix to ensure everything is synched. I have seen enough bugs over time that make me not trust MIDI in the final mix-down. With "unlimited" tracks, you are not losing anything by doing this other than the added step.

Are you using "fast bounce"on export?  Does it do it if you bounce in real time?
 
Try setting Edit - Preferences - Audio - Configuration file - BounceBuffSizeMsec to zero.

This is an interesting topic as last night I exported a track and when played back the piano part ( True Pianos) was lagging behind? 
It was a choppy 16th note groove so very noticeable. 
I re opened the project and it sounded fine...  I re exported and same issue??? 
So I froze the track just like you said and all is good. Now I'm paranoid that I've not been freezing MIDI tracks and all my old work might have this timing issue!!!! 
I mostly use a combination of TTS-1 and Session drummer and it's always sounded tight. Might be some VST's output differently. 

I am pretty sure this occurs also with a "real time" mix-down. Where I noticed it was I was duplicating another song, so left the original in track one (audio), and mostly MIDI for other tracks... there was a 1 bar delay to the song, and on any mix-down I tried, the MIDI tracks started immediately!! The work around listed above was the only way to make this not happen. I am pretty sure I tried every final mix-down option available.

I too have had timing/sync issues with recording mixdowns back into X2A.

[link=http://forum.cakewalk.com/tm.aspx?high=&m=2803672&mpage=1#2804832]http://forum.cakewalk.com...72&mpage=1#2804832[/link]

I have also had problems with session drummer crackling on long decay sounds when recording a mixdown but playback without recording would be OK