<type 'exceptions.SystemError'>: E:I wasn't able to locate file for the ttf-mscorefonts-installer package. This might mean you need to manually fix this package.

[Bashar]

I had just open Ubuntu Software Center and was trying to install the 'Ubuntu Restricted Extras' what this happened.

ProblemType: Crash
DistroRelease: Ubuntu 11.04
Package: aptdaemon 0.41+bzr614-0ubuntu1
ProcVersionSignature: Ubuntu 2.6.38-8.40-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
Annotation: Applying software changes failed
Architecture: i386
Date: Wed Apr 6 23:02:03 2011
DesktopFile: /usr/share/aptdaemon/aptdaemon.desktop
ExecutablePath: /usr/sbin/aptd
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Beta i386 (20110330)
SourcePackage: aptdaemon
Title: <type 'exceptions.SystemError'>: E:I wasn't able to locate file for the ttf-mscorefonts-installer package. This might mean you need to manually fix this package.
TransactionDepends: [[], [], [], [], [], [], []]
TransactionErrorCode: error-unknown
TransactionKwargs: {}
TransactionLocale: en_US.UTF8
TransactionOutput:

TransactionPackages: [[dbus.String(u'ubuntu-restricted-extras')], [], [], [], [], []]
TransactionRole: role-commit-packages
UpgradeStatus: No upgrade log present (probably fresh install)