threads within threads

Hi I am attempting to create a boost thread within an existing boost thread, i.e. a function called by the operator() function of an existing, running thread is attempting to make more threads. The new threads function objects are of the same type, but different from the parent function object type. This compiles and runs, but takes time equivalent to the threads running sequencially on a single thread. CPU usage indicates that both threads are running in parallel. Very strange... I am building with gcc v3.2.3 on red-hat linux build 2.4.20. Any ideas gratefully received!