How to expel an evil ghost from a macbook?

Question

Computer networks

Good afternoon, dear community, I don’t know what to do anymore.

My laptop is macbook air 2013. The problem has been persisting for a year and a half with OSX Lion and on updated Mavericks

Example 1 - house:

The apartment includes a 50 Mbit cord, it is inserted into the dir320 router that distributes the Internet ... Everyone has a normal and stable Internet connection, torrents download without restrictions.

Example 2 - parents' house:

A 100 Mbps cord enters the apartment, it is inserted into the apple router (I emphasize this point!) ...

Example 3 - office:

100 Mbps Internet comes into the office, it is inserted into the apple router (same as and in example 2), everyone has a stable Internet ...

The essence of the problem:
At the office, my laptop sometimes takes a long time to load sites, cannot determine the host. And this is the only laptop that does this. An experiment was carried out more than once, we put two laptops, mine and any other, my site loads, the second one is ok.
ALWAYS! on my laptop, any file from the torrent network downloads at a low speed (from 20 to 300 kb / s), and on any other laptop, if you connect the same torrent tracker for downloading at the same time, then we get the maximum speed on the line (minimum 1.5 mb / sec to 4 mb / sec)

The question is, what can it be in principle? Why is my laptop the only one with this problem? How to cure it?
I hope for your help, otherwise hands fall from the inability to understand this unknown phenomenon.
Thank you very much in advance.

Answer 1

boot from LiveCD and check hardware

Answer 2

Axis updated or set clean? If it's clean, then it was already suggested above to check the iron.

Answer 3

Try to specify the DNS servers on the computer manually, and not use the automatic ones received from the router.