[tex-live] tlmgr error, need help

[Ho Ho]

I got the following error

tlmgr: installation location http://mirror.hmc.edu/ctan/systems/texlive/tlnet/2008
Can't locate object method "expand_dependencies" via package  
"TeXLive::TLPDB" at /usr/texbin/tlmgr line 1037, <RETFH> line 116053.

It happens after a failed update and continue to appear each time I  
try to execute "sudo tlmgr update --all". I wonder how to solve it.  
Thanks.

BTW, during the failed update, some packages (including pdftex) are  
removed.