I can't delete comments. When I try to delete the comments in the backend, get a 503 error page and this message: "Service Temporarily Unavailable. The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later"

The error also appears when I click on sort by category, published, name ... etc.

Any ideas. I need help.
thanks

K2 v2.6.5
Joomla 2.5.9

Modalia.es