Process-resume hangs

The following simple test hangs in the call to process-resume (running
on "Version 1.0 (DarwinPPC32)"):

(in-package :common-lisp-user)

(defun simple-test ()
   (let ((process
          (ccl:process-run-function
              "Test"
            #'(lambda ()
                (format t "~&;; Suspending test process...~%")
                (finish-output)
                (ccl:process-suspend ccl:*current-process*)
                (format t "~&;; Resumed~%")
                (finish-output)))))
     (format t "~&;; Starting test...~%")
     ;; Allow plenty of time for test process to start up and suspend:
     (sleep 3)
     (format t "~&;; Resuming test process...~%")
     (finish-output)
     (ccl:process-resume process)
     (format t "~&;; Test completed.~%")))

(progn (trace ccl::%suspend-tcr)
        (trace ccl::%resume-tcr))

(simple-test)