I've heard of it before, but I've never experienced it before (thankfully!).
I played around with wording and the order of the wording in the search engine and came up with a few posts with info regarding ice mode. I don't know what glide mode is unless it's the same thing.
DJ Worm is the one that has been investigating it over the last few years. I would suggest contacting him about it directly. If anyone here has found out how to prevent it, I'm sure that he would be the one that knows about it.
Here's what I pulled up in the search engine if you want to take a look.
http://www.z06vette.com/forums/search.php?searchid=545794
Hope this helps.
Sal
PS. Where turn of what track did your buddy go off? If you want to keep it private, you can pm me. If you don't want to divulge that information, that's cool too. I don't want to know his name, but I'd like to know the circumstances.