There are forever questions about Codec Problems on this board. In a lot of cases this is caused by the fact that people are installing multiple codec packs. This is causing conflicts between them.
Please delete all codecs and packs before installing a new one.
If there is an option in the start menu, to uninstall the pack then use it. If not then go to add / remove software and remove all codecs or packs.
Do this before you add your new pack. In most cases this will solve your problem.