> while downlaoding a large website using the modified 
example(command line), httrack will halt at some 
uncertain point, no response to user except Ctrl-C, 
and doese not display any message any more.

Same problem using the WInHTTrack version? Also try to 
enable extended debuggind mode (verbose) using the -Z 
and -%H options to see if something strange happend in 
the logs.