The terminal window just disappeared after pressing enter…
Try again …
Hit Alt+F2 … in the input field type terminal and click the Run button… a terminal will open… When the terminal opens, enter the following command:
ls -a ~/.mozilla/plugins
hit the enter key … what is now displayed in the terminal ?
Ive got this:
[user@localhost ~]$ ls -a ~/.mozilla/plugins
ls: cannot access /home/user/.mozilla/plugins: No such file or directory
OK, if the terminal is still open, run these 5 commands (if not open one then run them):
(wait for each command to finish and leave you back at an $ prompt before running the next command)
Create a ~/.mozilla/plugins directory
mkdir ~/.mozilla/plugins
(this command may fail if the directory already exists… this is normal… just move on to the next command)
Change directory to ~/.mozilla/plugins :
cd ~/.mozilla/plugins
Use wget to download the flashplayer archive:
wget http://dl.dropbox.com/u/11876059/flashplayer11-32bit.tar.gz
Extract the libflashplayer.so file from the flashplayer achive:
tar -zxvf flashplayer11-32bit.tar.gz
Move the flashplayer archive back to your home folder to make it easier to delete if you wish:
mv -v flashplayer11-32bit.tar.gz ~/flashplayer11-32bit.tar.gz
You can now close the terminal.
Now close ALL running instances of Firefox, then reopen it… then go to this website:
http://www.adobe.com/software/flash/about/
where you can check which version of flashplayer you are currently using.
If that link says you are using a version older than 11.0.1.152… see below.
You may have to (in Firefox) go to Tools>Add-Ons>Plugins and make sure the only “Shockwave Flash” plugin that is enabled is the 11.0r1 one… and restart Firefox.
Once done, you can delete the flashplayer11-32bit.tar.gz file from your home directory, if you wish.
Sucess!! It worked now!!
Already running FP 11! Thanks a lot!
Dont know what I did wrong the first time but now it worked…!
Thank you very much!! 
No problem … glad I could help