okay, I was going to start a new thread about this, but realized that I posted this one two years ago. Since then I've encountered the problem in several versions of Logic (8 and 9) on several different machines in several studios. It's not consistent or predictable, but in addition to the mess described in my first two posts, I can add that sometimes when solo-ing a frozen track, another track will solo along with it. This also happens when using the "s" key to solo a highlighted track-another track will play along.
Un-freezing the tracks makes the problem go away.
I'm actually quite surprised that in two years, no one has responded to my posts...it doesn't seem likely, given the variety of versions and machines I've been using, that no one else has had this problem (?)