Hi bitman,
 
this could have 3 reasons: (1) software, (2) hardware, (3) something completely different ;-)
 
ad(1)
is what you are seeing happening on the latest Manchester build? If so, have you tried rolling back to a few releases earlier (because at least the 2 recent ones had optimizations included also to track solo functionality) ... so it might be worth checking whether this is software or hardware induced ...
 
ad(2)
soloed or not, disk load should be the same ... so i would not suspect hardware in the first place but it could be that you are at the limit with HD performance and just a little extra required from the software causes the inability to read all. however, this should be scalable i.e. archive 5%, 10%, 20% of tracks and see when audio drop out goes away ...
 
ad(3) something complete different ... the Monty-Pythonesque kind of problems ... the ones that do not make sense until you figure them out months later ... e.g. I got audio drop-outs exactly 59 seconds after the start of any song (actually as severe as an audio interface crash) and it took me a long time to realize that I for some stupid reason enabled "always echo current MIDI track" which caused a MIDI loop that took exactly 59 sec to overload all buffers ... took me 1.5 months to figure out. i'm not saying it's the same in your situation, but something done lately that you do not suspect in the first place could be causing all these troubles ...

It seems like ad3! - I like that one. :-)
 
Yes it's Manchester. - I know I could roll back a few revs to see if they broke solo on some platforms but in this context (Song Production) I don't feel like turning my DAW into a Gibson Brands test jig. I know that's a bad attitude to take today, but it's solo, not some super exclusive feature.
 
 I realize that mine is a special case or the forums would be lit up about this.
 
I didn't think of midi - I'll unplug everything and also check the midi settings.
 
Thanks for your help in this.
 
 
 

Ha! FreeFlyBerti triggered a similar memory of woe with the midi echo enabled..
But, I think I fixed a similar problem to yours with one of the Midi Preferences. I'm not at my machine and maybe someone else can help out with the exact description, but it's some preference for Midi Buffers I think. Increased it and all went smoothly. It was some time ago, so sorry for being so vague.
 
I also run, and have for some time now, my write and playback buffers sizes at 512.

I dinked with the buffers, this only delayed the inevitable by 10 or so more seconds.
Then I was staring at the FX button, thinking nooooooo.......
 
I clicked it.
Crap, now it plays with solo on.
I was of the mind (and still am) that if it sounds good it is good.
 
I'll try to find out which one(s) are to blame. - prolly the UAD-1 fx - ya think? :-)
 
Darn it. This song is all but done and it's a deuzy.
 

Ok we have a winner.
 
Today's problem vst for Sonar Manchester is:
 
The Klanghelm MJUCjr, Vari-mu comp all alone on the bass bus.
I've mailed Klanghelm Support.
 
Get it here:
http://www.klanghelm.com/MJUCjr.php
 
Glowing MixBusTV review:
https://www.youtube.com/watch?v=okuQHiURDZE
 
 Klanghelm Support said to update to the latest version as early adopters were treated to a denormal bug in the first offering.
 
That fixed it and now were all good as far as this issue is concerned.