Improved error handling in SilenceableWaveFile

Ignore-this: 4e81c7da491316a5853caab11c0d112a

darcs-hash:20100121114824-1e3d8-1753cb3e10a73923580c240c8c7ae31991e49fe2
Register SIPApplication for CFGSettingsObjectDidChange later to avoid races

Ignore-this: 895f60ae4f6bab1d093fa5f517ad0300

darcs-hash:20100121123113-1e3d8-8e8dcabc6e3bfe538689eb3a4f23dc69311313a4