The 3.21-4 release should fix many little problems, and 
especially some crashes and bugs. If you encounter a crash 
or a sudden error, please report it with:
- the context (URLs that caused the crash)
- the crash type (error message? or the program just 
disappeared?)
- the crash.txt file generated in the winhttrack program 
files directory, if any (if exists, it contains precious 
information to fix the bug)

Thanks!