Strange 404 errors?

Hello from Greece.

I get some strange errors on the 404 Monitor.

For example, I have the following page:

http://www.alternativerings-genie.eu/2012/10/30/siamo-tutti-greci

And I get 404 error for the following link:

http://www.alternativerings-genie.eu/2012/10/30/siamo-tutti-greci/cache/4e4055517809a8bbc8de1acb4ee9e560

The error is coming from several referers such as:

http://www.plentagos.com
http://sergeevs.eu
http://www.archidom.in

Why is this happening?

Thank you in advance,

Stratos Nikolaidis
Thessaloniki, Greece