Not getting notification of new K2 Comments anymore

The redirect component is a core-Joomla feature which lets you setup redirects from one URL to another. If it's using 256MB to load the redirects, it means there are many, many being stored there. I believe it may also show invalid/404 errors, which may be causing the huge amount of data. Either way, I don't think that's related to the issue.

There is no caching on the site. Regarding messing with the url's of the articles, that is something that is not very appealing, people link to these stories, this is a news magazine... Perhaps you can glean something from the information I have given you.

This was only for testing purposes. I was recommending to do it quickly, test, and then re-enable them. You can enable/disable SEF URLs from the Joomla -> Global Configuration area since it doesn't sound like any other 3rd party extensions are being used for SEF URLs.

..just to be sure, try again, and see if you still get the 500 error. The spam links appeared again in the index.php file for the second time. I have deleted them now, but perhaps that might explain the error.

Either way, there is still the mystery of how come the comments function works some days and some not. The spam links is not the explanation for that (since there were no spam links in that period).

The spam links are most likely the cause of everything. Not the links themselves, but the fact that someone has access to edit files within your system. That's very, very dangerous and really needs to be investigated by you or your host. The longer someone has access to edit files within your server, the more damage they can do. It's impossible to know if there has been more changes than just the ones in the index.php file. If they modified any files within JFBConnect, or any other extensions/code we rely on, that could easily be causing issues with our functionality.

I really can't express enough how important it is to figure out how the hackers are accessing your files and making modifications. You need to plug those holes, otherwise, we're chasing our tails on what may be wrong and, even if we do find the current issue, a new one may pop up the next time 'they' modify a file.

Thanks,
Alex