I am unfortunately saddled with a software package called Social Engine. Don't ever, ever buy it. It is extremely buggy and the tech support is beyond awful.
Anyway, I asked (paid even) them to do an upgrade and three days later (three days!) they finally did so. When I logged into the site I noticed that the styles were all missing. I opened a support ticket and all they told me was that it was a 416 error and to contact my ISP.
Since I am the ISP, I started doing my research only to find it's a rare error and I couldn't see any suggestions for turning range requesting off on my Ubuntu 10.10 Linode server (running latest Apache and PHP5 with APC extension installed).
this error was found by testing the direct link to the CSS files which are located in a themes folder in the buggy software.
Is this indeed a server fix I can leverage somehow, or is it something their software may be doing that I would need to look into more?