another tkinter question

[Ajay]

hi!

i have a main GUI class, which goes something like
class MainApp:
def __init__(self, master):
self.frame = Frame(master)
self.frame.pack()
...
now MainApp has a method evaluate() which calls a function, do_eval() in
another module. i pass the frame to do_eval to allow it to print error
messages using tkMessageBox.
the problem is when in do_eval i do
tkMessageBox.showerror("Info", ea.promptMessage, parent=self.frame)
here, nothing gets displayed at all. i hear the sound associated with error
messages, but no message box appears.

what am i doing wrong

thanks

cheers