Well for the first problem, you probably have ALSA installed as your sound system, and you probably have OSS for your output plugin. ALSA has to emulate OSS sound and sometimes it doesnt do a great job of it. (OSS is the old linux sound system, ALSA is the new standard).
Second problem, try typing make clean before any new configure or make. Otherwise old compiled object libraries will still hang arround. Other then that, what are you trying to do? Install GLIB? or install something that requires GLIB? Need a bit more info here...
I love emerge...I just typed emerge glib, and it downloaded, compiled, and installed everything.