I have a script that automatically updates from SVN. I was recently having crashes when compiling and it turns out that SVN doesn't update the ASM in FFMPEG. The fix, of course, is to do a "scons clean" before compiling forcing a recompile of the ASM. The down side is when you do that, it has to compile the whole thing over. Here is the code:
#This script assumes the directory BlenderSVN exists in your home directory
svn checkout https://svn.blender.org/svnroot/bf-blender/trunk/blender
chmod 755 bmake
This fixes the crashes when I update now....