can not update from bodhi (ubuntu 10.10 remix) to ubuntu

just as the title says when I try to convert bodhi linux (ubuntu remix) into ubuntu,it says as following:

sudo do-release-upgrade
Checking for a new ubuntu release
Done Upgrade tool signature
Done Upgrade tool
Done downloading
authenticate 'maverick.tar.gz' against 'maverick.tar.gz.gpg'
extracting 'maverick.tar.gz'
tar: Removing leading `/' from member names

Reading cache

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done

Updating repository information
WARNING: Failed to read mirror file

Third party sources disabled

Some third party entries in your sources.list were disabled. You can
re-enable them after the upgrade with the 'software-properties' tool
or your package manager.

95% [Working]
Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done

Calculating the changes

Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade:
The package 'update-manager-core' is marked for removal but it is in
the removal blacklist.

This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug against the
'update-manager' package and include the files in
/var/log/dist-upgrade/ in the bug report.

Restoring original system state

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: update-manager 1:0.134.12.1
ProcVersionSignature: Ubuntu 3.0.0-12.19-generic 3.0.4
Uname: Linux 3.0.0-12-generic i686
Architecture: i386
Date: Sat Mar 24 15:06:52 2012
GConfNonDefault:
 /apps/update-manager/check_new_release_ignore=
 /apps/update-manager/show_details=false
 /apps/update-manager/show_versions=false
InstallationMedia: Bodhi Linux - Release i386
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: update-manager
VarLogDistupgradeTermlog: