I just successfully manage to check out the Pyformex Trunk use the following command:
Previous attempts are all failed although I waited it for another day for Savannah to update SSH key.
Later when I re-check the process, I discovered that the SSH key my system(ubuntu11.10) generated is different from what is posted on the web page, which is "...oEb/ address@hidden " instead of ''...1Jpp0Q== address@hidden" .
So I changed the "/" into the "==" after the copy, then problems are solved.
Since other developers in the future may run into the same problem(especially who use Ubuntu instead of Debian GNU) , I send
this mail here.