Please try following to make sure if this error is related with template or it is a generic error with K2.
1. Try using another joomla template such as Beez3.
2. Rename following folder to "com_k2_test" which is a custom style for K2. This will make sure K2 is using its own default style.
templates/gk_league_news/html/com_k2
Let us know. See you around...