servimg doesn't work?

When I came down to my forum today, I realized that some category images and header were suddenly removed and their links were broken. I went down to servimg to check out what is going and get nothing but empty spots of these pictures. It's like they still existing but are not being shown and mysteriously can't be found.

This has been happened so many times and it is kind of frustrating.

What is going on? ;_;


// Edit. Sorry for bothering! I have found another topic related to this and check if there is anything that can answer these questions.