What sorts of things cause cyclic dependencies?

[Jonathan M Davis]

Okay. in the code that I'm working on at the moment, I get an exception saying 
that a cyclic dependency was detected but no information whatsoever as to where 
it is or what it means. I haven't been able to find much information on them 
other than some discussions of making it so that the compiler detects them at 
compile time. I have yet to figure out _what_ it is that is causes such errors. 
Could someone clue me in? It's really hard to track down a bug when the error 
only tells you that there's a bug and doesn't say anything about where it 
happens, and I have no clue what sort of things can be cyclically dependent.

- Jonathan M Davis