When I try to install K2 Ver.2.6.6 gives me the following error:

500 SQL = SHOW FULL COLUMNS FROM `y41s2_k2_categories`

Joomla version: 3.0.3.0.2

That may be happening?.

K2 directly download it from the official website.

thanks

It works fine for me.

I used Hostgator to install Joomla 3 and downloaded k2_v2.6.6 from the official site and installed it via Extension Manager.