Error #103 means Web Dumper was unable to resolve the address that was specified. A prime example of this would be a mistyped IP address, or a domain name of an unknown or unreachable host.
On the Windows operating system, error 103 can be produced by an anti-virus software. An anti-virus software may scan all the traffic on the http port 80 but since Web Dumper donwload lots of contents at the same time it may cause a great bottleneck. To avoid this problem you can simply uncheck your virus detection software while you are downloading a site with Web Dumper.