watchkreuznet@gmail.comImportError: cannot import name QPrinter

[wkm]

root@h1849258:/opt/calibre# ebook-convert --version
ebook-convert (calibre 0.8.11)
Created by: Kovid Goyal <kovid@kovidgoyal.net>

root@h1849258:/opt/calibre# uname -a
Linux h1849258 2.6.32-30-server #59-Ubuntu SMP Tue Mar 1 22:46:09 UTC 2011 x86_64 GNU/Linux

root@h1849258:/opt/calibre# cat /etc/issue
Ubuntu 10.04.2 LTS \n \l


root@h1849258:/opt/calibre# ./ebook-convert "/tmp/tmppi8kQN.html" "/tmp/tmpCrzq_X.epub" --level1-toc "//*[name()='h1']" --level2-toc "//*[name()='h2']" --level3-toc "//*[name()='h3']" --page-breaks-before "//*[name()='h1' or name()='h2']" --title "Dokumentationstest"
Traceback (most recent call last):
File "site.py", line 58, in main
File "site-packages/calibre/ebooks/conversion/cli.py", line 274, in main
File "site-packages/calibre/ebooks/conversion/cli.py", line 255, in create_option_parser
File "site-packages/calibre/ebooks/conversion/plumber.py", line 9, in <module>
File "site-packages/calibre/customize/ui.py", line 15, in <module>
File "site-packages/calibre/customize/builtins.py", line 531, in <module>
File "site-packages/calibre/ebooks/pdf/output.py", line 18, in <module>
File "site-packages/calibre/ebooks/pdf/writer.py", line 15, in <module>
File "site-packages/calibre/ebooks/pdf/pageoptions.py", line 6, in <module>
ImportError: cannot import name QPrinter

Why am I getting this error on Ubuntu 10.04.2 but not on 10.04.3?