> So was the problem only in the WinHttrack.exe shell, or 
in 
> the underlying httrack.exe too?
All releases had the problem ; it was a memory coruption in 
the root directory structure check. Time to time, the 
routine was corrupting other memory blocks, if the site was 
in a certain configuration (large sites, but also small 
sites)

> I recall that that 
> previously it appeared not to be happening when you were 
> using the httrack.exe command line version.  

The corruption is sometimes totally silent ; especially 
with the commandline release (because less blocks are 
touched)

> Anyway, I'm glad something has been found.  The other 
> question is would the mentioned 'bad' writing that caused 
> heap problems have corrupted any specific downloads from 
> sites?  Anything specific to look for?
No no, the only risk was the crashes ; the routine was only 
corrupting blocks immediately after the structcheck blocks 

BTW, please update to 3.21-7, I had to "emergency" fix 
another bug (directory strcutures NOT created at all, 
causing logfiles NOT to be created!)