The file surely exists... Are you using the 'cat' command or just calling a file from the command line?
This error typically happens when a package was badly installed. Possibly you shutdown the computer while it was installing? (Electricity went off?)
The way to fix that is to remove the status from the file /var/lib/dpkg/status. To edit the file remember the 'gksudo gedit' command?
Now I would strongly advice against you editing this conf file on your own. Great errors can ensue if you do something wrong.
I found this
post on a blog. Read it, and look at what he deletes in step 6. Delete the same thing.
Then remove the package flashplugin-nonfree (sudo apt-get remove flashplugin-nonfree) and reinstall it (sudo apt-get install flashplugin-nonfree).
Problem should be solved.
PS I really recommend you read a tutorial on linux. While I still maintain that it is a very easy system to use, you won't know how to use it unless you read a "manual". You can try to discover it on your own, but you'll find that very difficult and disappointing, especially if you've never worked on a Unix system before.