marshal.loads ValueError

[abcd]

I have the following code which is sent over the wire as a string...

from time import time
class Foo:
    def go(self):
        print "Time:", time()


I get this code and store it as, "data"

data = receivePythonSource()

Then I try...

exec marshal.loads(data) in my_module.__dict__

However I get an error saying:
ValueError: invalid literal for __float__: om time import time
class Foo:
    def go(self):

....almost like when I try to marshal and exec it misses the first two
characters, "fr" ...any ideas?