Adobe Flash may not be coming to Linux, but will to Mac OSX.

I too have terrible problems with Adobe Flash and Firefox but
everything works fine in Opera or Chrome so it's not Flash on the PC
that's the problem but the plugin for Firefox. Even removed Firefox
totally using Synaptic and put back, plus replaced the plugin file -
no dice, Firefox refuses to play flash video :-(

I'm hanging fire on doing any more about it until 12.04LTS is out and
evaluating the switch to it. Having other browsers that work means
it's not such an issue, if mildly annoying

Adobe is discontinuing development of Flash for Linux. It is a good idea
not to try to upgrade unless things aren't working well. You will not have
to wait till 12.04 because you cannot expect any change since Flash is
proprietary software.

Chrome does not require you to install Flash. It comes with it built in.
Firefox will need you to install Flash. You do not say what file format it
is. If it is a .deb file then you can click on it and it will open in
either Software Centre or Gdebi depending on your version of Ubuntu.
However, if it is a binary file then you will have to make it
executable first. To do that you right click and go to Properties and check
the box on the r Permissions tab to make it executable.

If all fails then completely remove Flash using Synaptic. Then clean the
cache and re-install. If you do not clear the cache then it will just
re-install what you have already downloaded rather than get a fresh copy.

The command for cleaning the cache is sudo apt-get clean. If you are on
dial-up this is probably not a good idea since it will remove the
downloaded copied of all installed debs. If you are short on HD space on
your home folder this is a good command to remember to free up disk space.
If you only want to remove one package then use sudo nautilus (or sudo
dolphin for KDE) from a terminal. Then navigate to /var/cache/apt/archives/
in the root directory and remove the one package.

If this is way too much for you then try Chromium which is in
the repositories or Chrome from Google.

Flash isn't going away soon, Adobe are still providing security
updates for the next 5 years, and Google is adding it into Chrome
directly under their own plugin ( sanctioned by Adobe ). All a bit of
a mess overall with Flash and it not being even developed for the
mobile platforms at all now - not that it'll be missed I guess, apart
from the hassles it gives us it's a memory hog and has seen some major
security holes ( no doubt others will be found too before it totally
disappears ! ).

Not a huge problem not having it working in Firefox and it won't be if
12.04LTS also has the same problem with it :-)

Flash for Linux will be frozen at v. 11.2. I am not being alarmist. Just
saying not to expect Ubuntu 12.04 to be the savior. I expect Flash to work
but there will come a time when it won't work on all sites. Not sure when
that will be, but hopefully HTML 5 will work by then.

I install Ubuntu, I install the Restricted Extras, flash works. (And I try every
version as it appears, usually trying several variants, eg. Ubuntu, Kubuntu,
Lubuntu, Mint, spread across two desktops and a laptop.)

That's what usually happens with me but this current install of
10.04LTS 64 bit isn't playing ball with flash on Firefox for some
unknown reason. I could just do the install all over again but since
this is planned for 12.04LTS and it's not too far off now I'm just
leaving Firefox 'flashless' and not worrying too much about it :-)

g> I install Ubuntu, I install the Restricted Extras, flash works.