Wave Profiler is a good thing to run whenever you change buffer settings or audio card configuration. It is located under Options - Audio. Basically, it figures out the inherent latency in the system and compensates it so your audio tracks will line up while over-dubbing or adding midi tracks. It determines the latency of the current settings (and will change the displayed latency in Options - Audio - General) and also sets the optimal buffer settings in Driver Profiles.