I'm waiting for a plane and browsing this forum and it has finally occurred to me to post on this common issue for me. 

I generally have two or three tracks associated with bass guitar. I'll have an amp, a DI and sometimes a an alternate input of some kind like a sansamp. They are usually all sent to one bus where I will have a sonitus compressor setup to be keyed by the kick. Sometimes this setup works just fine and I can open and close the project without issue. Other times when I re-open the project the bass will be all grumbly and glitchy sounding. If I solo to bass bus I can hear the heavily messed up sound playing back. If I open the compressor on the bus and click the button that toggles between Audio and Input (I think) it will play back this totally fragmented non-musical sound of bleeps and bloops and spits and pops. When I toggle back and and restart the playback everything will be fine from there.

It has done it on Sonar 8.53 Producer and X1 Producer Expaned for sure. I am running X1 now. I can't remember when I started noticing it but it's been happening for at least two years or more. I've never complained because the workaround is only a minor inconvenience. 

I have had this problem with several interfaces including MOTU, M-Audio and Tascam.
I am running Windows XP SP3

This is the only compressor I use for Sidechaining and it seems to only happen between the kick and the bass but not with other instruments. Sometimes I will trigger directly from the kick track or from a bus that the kick is feeding. I will sometimes key a sidechain on other instruments from the lead vocal or something like that and I don't have the problem there. The only thing I can think of that I do differently with the kick/bass sidechain and I generally set the attack 0ms where on other cases I will have a slower attack time.

Okay, my flight is about to board so maybe I will arrive at home with a solution, explanation or comiseration awaiting. 

Cheers, William

ive noticed soloing buses can be finiky. have you solod the travks feeding the bus? same result?

Doesn't matter where the solo initiates from, Bus or Track, one of the group or all, the glitching continues until I monitor the key input through the compressor and then switch back to audio. Once I do that all is fine for the rest of the session. Once a project does this it will always do it when I first open it. Occasionally I can fix it by creating a new bus and moving rerouting things, sometimes it doesn't fix it.