Sometimes clicking on the page links of http://lgames.sourceforge.net/ makes my browser to promt me to download the ".php" file.
I am a developer myself and have seen this error before. When I remember correctly, it leads to a misconfiguration of the server. However I only can see the result and no logs and configs, so your problem could be totally different (e.g. a temporary network packet fragmentation issue).
When I download the file (I tried "about.php") it is just an empty file.
The error occurs randomly and is therefore hardly reproducible. One has to click many times on different pages to reproduce it.
I thought you should know about it.