I can not install anything with macport

[sara iodice]

I have a mac book pro with mac OS X 10.6.7.
I can not install anything with macport.

For example, if I try to execute "sudo port install opencv", I have this
error:

''--->  Installing bzip2 @1.0.6_0
Error: Target org.macports.install returned: /usr/bin/tar: invalid option
-- q
Try `/usr/bin/tar --help' for more information.
Error: Failed to install bzip2''

'''This is the log file:'''

''version:1
:debug:main changing euid/egid - current euid: 0 - current egid: 0
:debug:main egid changed to: 501
:debug:main euid changed to: 502
:debug:main Executing org.macports.main (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.archivefetch (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.fetch (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.checksum (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.extract (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.patch (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.configure (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.build (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:main Skipping completed org.macports.destroot (bzip2)
:debug:main Privilege de-escalation not attempted as not running as root.
:debug:install install phase started at Thu Aug 25 15:08:06 CEST 2011
:notice:install --->  Installing bzip2 @1.0.6_0
:debug:install Can't run install on this port without elevated privileges.
Escalating privileges back to root.
:debug:install euid changed to: 0. egid changed to: 0.
:debug:install Executing org.macports.install (bzip2)
:error:install Target org.macports.install returned: /usr/bin/tar: invalid
option -- q
Try `/usr/bin/tar --help' for more information.
:debug:install Backtrace: /usr/bin/tar: invalid option -- q
Try `/usr/bin/tar --help' for more information.
    while executing
"exec [findBinary tar ${portutil::autoconf::tar_path}] -xOj${qflag}f
$location +CONTENTS"
    (procedure "extract_contents" line 6)
    invoked from within
"extract_contents $location $portarchivetype"
    (procedure "portinstall::install_main" line 19)
    invoked from within
"$procedure $targetname"
:info:install Warning: the following items did not execute (for bzip2):
org.macports.activate org.macports.install
:error:install Failed to install bzip2
:notice:install Log for bzip2 is at:
/opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_archivers_bzip2/bzip2/main.log
''

== Please, help me ... ==
Thanks