This gets curiouser and curiouser!

(L)PCM audio is the rock standard audio for DVDs -- and is also the audio format for video captured in DV format from a mini DV digital video camera. If you can capture DV and hear audio, then the codec is there ... or should be. On my system (just checked with Sherlock) it is associated with DirectShow Runtime and is supplied by Microsoft in the standard quartz.dll file in the system32 sub-directory of Windows.
As for the anomaly at 100%, I cannot account for it. While I don't use multitrim either (and in fact have never done so, even to experiment), I have no trouble with audio playback of clips trimmed with the scissors and played at 100%. The only audio format I have ever had trouble with was in fact MP3 produced with the LAME codec...