I've just started using Quark 4.0 in classic mode under Jaguar. It's surprisingly working quite well. However, if the Mac goes to sleep, when awoken all the functions in Quark become inaccessible, only the 'append' in the file menu is available if no docs are open, alternately just the 'save' & 'save as' are available with a document open.
The document itself is untouchable, nothing works.
If I quit and restart Quark, things are fine again.
Sometimes there's a brief flash of a os 9 yellow finder alert window, but I see no text in it.
This isn't a deal breaker, since the 'save' has always been available, and restarting Quark is pretty quick.
I'm using Extensis Suitcase 10.1 in both Jag and Classic (with the bridge extentsion).