How often are you switching workspaces before you get a crash?
I set my WorkspaceExpireTime to 15.5 seconds via
Code:
defaults write com.omnigroup.OmniWeb5 WorkspaceExpireTime -float 15.5
and started switching between some of my smaller workspaces. I didn't have any trouble causing the footprint to climb, as seen here:
Crash immediately followed.
Perhaps the high-water mark keeps getting bumped higher and higher until the address space is exhausted, even if the amount of memory in use isn't as high (though in my snapshot, there's a pretty hefty memory footprint, too!)