I have started having problems with my VPS in the way that it would faill to serve the pages on all the websites. It just showed a blank page, or offered to download the php file ( luckily the code was not in the download file :) ). The server was still running, but this seemed to be a problem with PHP, since i could login into WHM.

If i did a apache restart, the sites would work again.

After some talks with the server support they told me this is a problem with the APC extension witch they considered to be old and not recommended for production servers. So they removed it for now, to see if the same kind of fails would continue to appear.

I haven't read anywhere that APC could have some problems or that its not always recommended to use, quite the contrary ... everywhere people are saying to always use it.

The APC extension was installed ssh and is the latest version.

Edit: They also dont recomend MemCache and say that a more reliable extension would be eAccelerator