Newbie having issues with threads

I'm a newbie trying to write a script that uses threads. I'm right now
a little bit stuck in understanding why the code snippet I wrote doesn't
seem to be entering the function defined in the start_new_thread() call.

If I run it as is (the threaded version), the output is:

UA_1 configuring...
UA_1 halting..

But if I comment out the line w/ the thread and just call the function
directly, everything seems to work OK:

UA_1 configuring...
UA_1 executing...
UA_1 halting...

Can anyone tell me why the thread doesn't seem to invoke the function
"execute()"? I'm running Python 2.4.3.

Here is my code:

===========
import thread

class Test(object):
def __init__(self, instanceID):
self.instanceID = instanceID
def configure(self):
print self.instanceID + " configuring..."
def execute(self):
print self.instanceID + " executing..."
def halt(self):
print self.instanceID + " halting..."

if __name__ == "__main__":
"""usage: sipp_auto [options]"""

ua1 = Test("UA_1")

ua1.configure()

#ua1.execute()
thread.start_new_thread(ua1.execute, ())

ua1.halt()

===========
Thanks, James