sugar-session-0.88 and sugar-emulator-0.88 crash after upgrading to 0.88.0-4

Operating System: Ubuntu Lucid Lynx (10.04) x86
Kernel: 2.6.32-22-generic
Python: 2.6.5
sugar-session-0.88: 0.88.0-4
sugar-emulator-0.88: 0.88.0-4
xserver-xephyr: 2:1.7.6-2ubuntu7

15 hours ago I installed sugar-session, sugar-emulator as well as xserver-xephyr and I could run sugar-emulator normally, thought I had some problems with keyboard grabbing. 4 hours ago, I ran automatic-update in my Ubuntu, the softwares which were updated included sugar-session and sugar-emulator. After updating and restarting my Ubuntu box, I couldn't run sugar emulator and suger-session again. When I chose Sugar as my session to log in, the screen flashed for 3 seconds and it took me back to the log in screen. I logged in with GNOME and try to run sugar-emulator (with xephyr as the server -- if I was not wrong) with the command: "/usr/bin/sugar-emulator", I bumped into the following error:

  File "<string>", line 1, in <module>
  File "/usr/lib/python2.6/dist-packages/jarabe/util/emulator.py", line 26, in <module>
    from sugar import env

I had tried to reinstall those 4 packages but it didn't help. Is this a bug of sugar or python? I would be so glad if there is any help. I am a Sugar developer for the XO machine.

Edited: Correct bad English, sorry.