100% CPU usage while using ccRTP SingleRTPSessionPool

In my application I have several RTP sessions but want to use only one 
thread to manage them. Therefore I use a SingleRTPSessionPool and add 
RTPSessionBase objects for each session.

My problem is that once I start the pool thread it utilizes 100%
of the CPU time. Even the following two simple lines, which do not even 
add an RTPSessionsBase object to the pool, result in that behaviour:

   SingleRTPSessionPool test;
   test.startRunning();

I tried to localize the responsible code fragment. Obviously it has to
be somewhere in the run() method of SingleRTPSessionPool. The code
blocks in the select() call until a specific timeout occurs. But 
blocking is fine, that doesn't lead to CPU utilization.

Has anybody else encountered such a problem? A SingleRTPSessionPool demo 
in a future ccRTP release would be great.

Regards
Jonas