readline() after popen hangs

[Thomas Steffen]

Hallo,

here my code: 
...
(sin, souterr) = os.popen4(command)
while 1:
  line = souterr.readline()
  print line
  if not line:
      break
...

Now I have the problem: the last two lines are written after five
(5!!!) minutes. Why so a long time?

Who has a solution for this problem?
Thank you for your hints, Thomas