> 3. all ok, downloading
> 4. disconnecting from Internet
> 5. Numbers in Links Scanned begins growing up very fast 
with 
> each 'error -5'. why? 

Becaue httrack gets "unable to connect" or "no route to 
host" or "dns error" errors due to connection outage and 
attempt to retry the connections (which also fails), 
increasing the number of tried links.

There are no real solutions except detecting per-OS 
connection status (not easy to do, for example when you 
have a NAT firewall which is "down")