> Something happens when is scanning because after a while 
> appears only errors.

Hum, maybe a filter against offline browsers?
First if you want only a part of the site, use filters (set 
options/scan rules)
Then, use bandwidth limit NOT to overload the server (see 
in options), and a maximum of 1 or 2 simultaneous 
connections. This should reduce the load, and allow you to 
capture the site.

But there might be also a bug either in the parsing, or in 
the site (loops?), depending on the remote structure