OpenAL and Popping Artifacts

I am using OpenAL for a music application for the iPad. Before that, it worked fine, but now, after updating my device to iOS 4.3, noise appears during playback. They become apparent when playing several samples (i.e. Chords) and occur at the beginning of a new sample after the 1st or 2nd samples have already been played. Besides these artifacts, the rest of the audio output is normal.

I buffer the audio data for each instrument, create a source for each reproduced sound, and attach the source to the cached buffer. Buffer connected to sample audio using alBufferDataStaticProc ()

I also changed AL_FREQUENCY of the AL context to match the file sampling rate (16 kHz), but this only fixes the problem when the sample (source) to be played has an AL_PITCH value of 1. So some if you change AL_PITCH, you change the output frequency of the source that will not match the output frequency of the AL context, causing a problem

Some of the code is borrowed from Finch, which does a lot of data initialization. Here is the source code url: https://github.com/zoul/Finch

I look forward to any pointers.