'apt-get' always fails with ERROR 404: Not Found over a package (flashplugin-downloader)

Question

the following error is preventing me from installing anything on Xubuntu 11.10. How can I fix it??

$ sudo apt-get install meld
Reading package lists... Done
Building dependency tree       
Reading state information... Done
meld is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]? Y
Setting up flashplugin-downloader (11.0.1.152ubuntu1) ...
Downloading...
--2012-02-06 21:23:36--  http://archive.canonical.com/pool/partner/a/adobe-flashplugin/adobe-flashplugin_11.0.1.152.orig.tar.gz
Resolving archive.canonical.com... 91.189.88.33
Connecting to archive.canonical.com|91.189.88.33|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2012-02-06 21:23:36 ERROR 404: Not Found.

download failed
The Flash plugin is NOT installed.
dpkg: error processing flashplugin-downloader (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 flashplugin-downloader
E: Sub-process /usr/bin/dpkg returned an error code (1)

Answer 1

flashplugin-downloader is a package from the multiverse repositories. Version 11.0.1.152ubuntu1 is from 7 October 2011 and has been superseded by version 11.1.102.55ubuntu0.11.10.1, released on 11 November 2011 (source).

Some possible causes:

• you haven't refreshed your packages list for a a while (sudo apt-get update)
• you're using a mirror that is down or not updated. See How can I get apt to use a mirror close to me, or choose a faster mirror? for a way to change mirrors

Instead of using the flashplugin-downloader package, I suggest you to install Flash as described on How do I install Adobe Flash player?