(re: Quest for Glory 4 freeze up) The problem is that modern computers are too fast for certain parts in old SCI-1 games, such as QFG4 and GK1. There are several Slow Down utilities available on the web, but there is but one that will get you past the dreaded Error 52/Swamp bug: CPU Killer, it’s available here;
Slow down your computer BEFORE you enter the swamp. Fight and kill the Chernovy, take the ritual, and leave the area.
On a side note; Something that is often mistaken for a bug in the Swamp area, is when the screen turns completely black after casting Reversal. This isn’t a bug, but a Darkness Spell cast by the chernovy. 🙂 In this case, cast Juggling Lights.