Multiple Problems, gtk+ related?
 

I have many many problems. The ones I can think of are:

Firefox, and Opera randomly crash, firefox much more so than opera
Cannot compile many things, errors often related to Pango, or GTK+ 2.0 not being found even though they are there.
I did not used to have these problem compiling the exact same things.
There are many more, but I cannot think of them right off hand.

I tried to upgrade my version of GTK+, and in the process I may have installed newer versions of pango, and cairo and possible some other dependencies too, I do not remember. I compiled all of these from source. I am not sure exactly what I did, I probably have multiple versions of some things installed now.

If possible and this would work, could I just go and remove everything I have, that being pango, cairo, gtk, and such and just recompile them from scratch or will this not work? I'm not sure what to do short of reinstalling Slackware. I would like to avoid that, if for nothing else so that I could actually learn more by fixing this.

If I do have multiple versions of things installed, I know that this normally is not a problem, but if I were to install something that is requires say gtk2, how would I tell it of the mutiple versions installed, which one to use?