Spent a really frustrating hour or two this weekend figuring out why Apache 2.1 wasn't working on vallista.idyll.org.
The symptoms of the problem were that Apache would not serve static pages at all. I could serve dynamic pages (in fact, I "patched" my few static sites by turning XBitHack On so that they would be served as INCLUDE files) but I couldn't serve any static files. .html files, .css files, .jpg/.png files: all would come up blank. Literally, blank: Apache was serving no content whatsoever.
I finally figured out that files above 255 bytes in size were being truncated at 0 bytes, which led me (via Google) to this post. Turns out that sendfile apparently doesn't work on my VPS, either. Grr.
So basically I blew a huge amount of time on a silly little problem. Sounds like sysadminning to me...
The end result, however, was that I reduced my standing memory usage from over 375 mb to under 210 mb by switching from multiple SCGI servers to multiple FCGI servers. Good stuff.