I'm doing a mix with 40 tracks.
Every time I stop, make a few changes or save, the hourglass kicks in and I have to wait for maybe 3 or more min. for it to return control to me.
Why would this be?

Need more information Glenn.
 
Is it every time you stop? (Autosave kicking in?)
Is it when you make a few changes?
Is it when you save?
 
Or combinations of the above?
 
Are your 40 tracks all audio or a combination of Audio/Midi?
If there's any Midi, what synths, soft or external are you driving?
 
Also, re your signature - do you mean your rig is operating with 2Gb of RAM?
If so, I would suggest this is what's bottlenecking your CPU

Thanks Jonesey.
You are probably right it feels like a RAM thing (I'm XP 32 bit) but why now?
It's been working fine with midi etc on other files.
The tracks are all audio, no midi
It feels like autosave so I set that to 20 min or 40 changes -no joy.
I think it varies but seems like I get maybe 10 changes and it goes hourglass for several minutes.
Definitely when I save but not as long.
I took a huge video off the desktop (Karl's $8 instructional) and uninstalled several unnecessary programs just in case tho that should only be disk memory.
I'm now defragging and cleaning up the 2 HD's that have Sonar on them.

Maybe it's a function of how big the project file is, or whether it's a cwp or cwb.