Problem with alSourceUnqueueBuffers

I am trying to implement a streaming sound engine with OpenAL by uploading small blocks of sound data into buffers as needed instead of the entire sound at once. Doing this requires a lot of buffers queued onto one source so I tried to reuse processed buffers when available instead of creating a new buffer for each block of data. The update loop looks something like this...

alGetSourceiv( source, AL_BUFFERS_PROCESSED, &count );

if ( count ) {
        alSourceUnqueueBuffers( source, 1, &buffer );
} else {
        alGenBuffers( 1, &buffer );
}

alBufferData( buffer, ... );
alSourceQueueBuffers( source, 1, buffer );

It seems that whenever I use alSourceUnqueueBuffers the source is stopped or otherwise no longer plays the data queued. This causes any sounds longer than the initial few buffers (about two tenths of a second worth) to stop or fail to play entirely. Even if not using the buffer from alSourceUnqueueBuffers  or calling alSourcePlay afterwards the problem persists. No errors are being generated. This problem can be circumvented by not calling alSourceUnqueueBuffers and generating new buffers for each sound segment.

The questions I have are, is there a significant performance gain from uploading one buffer per source as opposed to uploading segments at a time? Is there some functionality of alSourceUnqueueBuffers that I am missing which is causing this problem?