Yes, the flash plugin often seems to cause problems with firefox. It crashed mine several times last night. It just seems to be unstable. I blame it on the closed-source nature of the plugin.
As for your compilation, your problem is spelled out for you clearly in the last lines of your output:
checking for LIBSNDFILE... configure: error: Package requirements ( sndfile >= 1.0.10 ) were not met:
No package 'sndfile' found
And then it goes on to give you some possible fixes. So first make sure you have libsndfile and libsndfile-dev installed (or whatever they're called in your distro).