For months we have been struggling with a weird issue on 1 of our WordPress Network installations. We have 4 installations on 1 VPS and only one of the four installations generates this error.
The problem is that pages on all sites that run on that WordPress Network installation, randomly(?) seem to try and parse the page as being RSS content. See this screenshot: 
Full image
This only happens once per session (if it does at all) and after refreshing the page, all is good. This makes it extremely hard to fix, because debugging is almost impossible.
Whenever the issue seems to appear, the (RSS) content that is being displayed, is that of a different page..
Could this be a WordPress issue, or could this be an issue in the Apache config?
Some domains we are encountering this on:
I hope there is someone that could help me solve this issue!
Update:
I just had the issue on the page: http://www.skynetsg.co.za/peter-sserwanga/ that was newly created. I checked the apache logs and they show nothing strange, just a 200 OK header..
Below is a link that may fix your problem. If your running WHM/Cpanel, you may have to recompile apache with out certain modules.
rss-feed-displayed-instead-of-html-page