Can no longer play videos in Ubuntu

[missionary7]

Things were working fine a few days ago. Now, whenever I try to play any video on my computer, I get the error message:

No suitable decoder module:
VLC does not support the audio or video format "h264".
Unfortunately there is no way for you to fix this.

This is happening even with videos that I have played countless times before. I'm guessing it's not a problem with VLC specifically, because I tried with a couple other video players also, and got a similar message. But since VLC is the player I use (almost exclusively), and since I don't know what might be REALLY causing the problem, I thought I'd ask here first. I'm running Ubuntu 12.04 LTS.

I'm pretty new to Linux, so if you can give me instruction Crayola style, that'd be great.

Thanks!

[Jean-Baptiste Kempf]

You probably did break your VLC installation, including your libavcodec one. You need to reinstall.

[missionary7]

I did reinstall, but it didn't help.

[Bell]

I also have such problem, But it didn't help me

[PCMarc]

I suggest you to do:
sudo apt-get install ubuntu-restricted-extras
and try to reset settings, type in terminal:
vlc --reset-config

Let me know if it works, but I'm positive it will.

Best Regards,
DekoG