After a bit more experimentation, I discovered that the frozen executable
from test runtime008 can fail with an argument as little as "2"
(2 iterations of the loop).  Leaks with such a small number of iterations
are much more likely if the system is loaded.  I artificially loaded it
by running a number of executions in parallel.

I also found that most of the time when a test fails, there are two
leaks displayed.  A typical one is:

Iteration 57   Found leak: (curr - prev=922104) (curr - first=922104)
Iteration 58   Found leak: (curr - prev=-922104) (curr - first=0)

(Note that I modified the original test to display which iteration it is on).

To reproduce, you can use the attached "runtime008" script.
First run test runtime008 with -keep option.
Then modify the line at the beginning of the attached script to set the correct
path to the executable and the desired number of iterations (first argument
to the executable).

Then execute the script via (from csh):

   source runtime008 > my_output1 &

To run additional copies in parallel to create more load on the system, if 
you aren't seeing any leaks:

   source runtime008 > my_output2 &
   ... (as many as you like)