Just tried to install the 10.5 version of macports on a 10.4.10 machine and got the error:

can't find package Pextlib 1.0

    while executing

"package require Pextlib 1.0"

    (procedure "mportinit" line 365)

    invoked from within

"mportinit ui_options global_options global_variations"

Error: /opt/local/bin/port: Failed to initialize MacPorts, can't find package Pextlib 1.0

pextlib.dylib is located in /opt/local/share/macports/tcl/pextlib1.0/ 

thoughts? no help in tickets they referred the question here