problem with these packages: libavformat52 & gstreamer0.10-ffmpeg

<p>In Synaptic Package Manger I get this error: E: libavformat52: subprocess installed post-installation script returned error exit status 2 E: gstreamer0.10-ffmpeg: dependency problems - leaving unconfigured</p> <p>In terminal I get this error: Errors were encountered while processing: libavformat52 gstreamer0.10-ffmpeg</p> <p>My Firefox runs horrible and I think the above could be related. Firefox is slow and freezes so much it's virtually impossible to use. What I would like to do is remove every component of it, and all these codecs and start fresh, but I don't know how. I really don't know much about terminal, so please consider that when giving advice. I have a few add-ons in Firefox like Session Manger, IM Translator, and Scrapebook, (although it is uninstalled now)</p> <p>I thought maybe an upgrade would help so yesterday I went from 9.0.4 Ubuntu to 10.04...I did a clean install from a CD and reformatted my root folder. I did try Ubuntu9.10 some months ago, but had tons of trouble with the graphics card resolution.</p> <p>My computer is a desktop Acer AMD Athlon(tm) 64 X2 Dual Core Processor 3800+, GeForce 6100 nForce 405, MCP61 High Definition Audio, 1G Memory DDR2</p>