Restoring the default settings for Audition CS6

Question

Fortunately you don't have to uninstall and reinstall Audition to do this - although that's certainly an option. Bear in mind that doing this will only work if you choose to delete your preferences as part of the process.
There are several other options though, and I suggest reading through all of them before deciding which to use. We'll start, though, with the other simple one. If you start Audition with the 'shift' key held down, this will achieve the same result - the preference files won't be read, and the default (aka 'vanilla') ones will be reinstated. Certainly with a Mac (and probably a PC as well) you have to hold the 'shift' key down at least until the splash screen appears, otherwise it might not work.
From here on, it gets a little more complicated, but you get more options. The reason for this is that in order to get at the individual preference files, we have to consider three different operating systems, XP, Windows 7, and OS X. By default, in all of them, the location of these files is hidden, and you have to reveal it. When you have done this, the path and files will be revealed.
Revealing hidden folders:
XP: In a folder, go to Tools>Folder Options>View and scroll down to the hidden folders entry. Select the 'Show' option. The path to the Preferences folder is C:\Documents and Settings\[user_name]\Application Data\Adobe\Audition\5.0
Windows 7: In a folder, go to Organise>Folders and Search Options>View, and then it's the same as XP. The path to the Preferences folder is c:\Users\[username]\AppData\Roaming\Adobe\Audition\5.0
Mac OX: The Preferences are in a library folder, and are apparently stored twice. The locations of them are:
/Users/[User_Name]/Library/Preferences/Adobe/Audition/5.0/
/Users/[User_Name]/Library/Preferences/com.Adobe.Audition.5.0.plist
There is a note about this at the end of this FAQ*.
Anyway, there are, apparently, several ways to unhide them:
1. The easiest way to get there without opening Terminal is to open Finder or click on your desktop, click Go in the menu bar, then hold down the OPTION/ALT key.  You should see Library appear in the menu as long as your holding that key and clicking the menu item will bring it up in Finder.
2. Use Command+Shift+G from the Mac desktop (or Finder>Go>Go to Folder) and type in ~/Library to temporarily access the Library directory. When you have finished manipulating the relevant parts of it, close this window and the folder will no longer be visible.
3. To make the Library folder visible permanently (like in OS 10.6 and earlier), open the Terminal application and use the following command: chflags nohidden ~/Library/
What do you have to do when you've revealed the folder?
The basic idea is that if Audition opens, and it doesn't find a particular file in the preferences folder, it recreates it. So, you can either delete all the files in it (the same as Shift+open), or you can be more selective. Primarily there are three .xml files that you are interested in, and if you are only having a problem with one of them, then that's the only one you need to delete.
Application Settings - deleting this will restore most of the settings in the program itself back to defaults
Effect Presets - deleting this will restore default settings, but if you have made any of your own presets, you will lose these too.
Favorites - the same as Effect Presets, only for the Favorites list.
There is also an .xml file for Machine-specific settings, but this only affects your sound device, and generally would be rewritten anyway if anything changed, so generally doesn't need to be touched. Mainly it's the three I mention above that are the ones you will be interested in.
* A note from Durin about the Mac preferences files:
"The directory path, ~/Library/Preferences/Adobe/Audition/5.0/ is where we store all the preferences, presets, workspaces, log files, etc.  Anything and everything a user may need access to.  The .plist file is more of an application/OS level preferences - similar to an ini or registry entry in that it's less user-facing and more preferences for how the application works with the OS.  In Audition's case, this stores information such as the last directory accessed, File Open/Save dialog dimensions, and other mysterious prefs that are just random GUIDs that Audition and OS X understand. 
In either case, if the directory or .plist is missing, it will be rebuilt on launch to the first-launch defaults."

Answer 1

The success of setting the correct cassette will depend on the applications you use. If the apps are set to use any cassette, rather than call a particular cassette, then making cassette 2 the default will succeed. But if the app calls cassette 1, then no amount of driver default settings will help. So in this case, you will have more success if you create another preset for printing to cassette 2, then you can ensure you select this preset when you want to print on plain paper. And of course you can select the envelope preset when you want to do this.
If you do want to look at modifying the printer defaults, this can be done via the CUPS web page.
To access CUPS, open Safari and type
http://127.0.0.1:631/printers
This will open the CUPS Printer administration page and will show all the printers currently configured on the Mac. For the printer that you wish to change the defaults for, click its name in the Queue Name column.
Clicking the printer name will open the printer administration page for that printer. Here you need to click on the Administration drop menu and then select Set Default Options.
This will show a new page with four menu headings (links); Options Installed, General, Banners and Policies. Select General. Scroll down the list until you find an entry like "Paper Source" or something similar that shows the cassettes and select Cassette 2.
With the option selected you then need to scroll down the list to the bottom of the page where you will see the ‘Set Default Options’ button. Click this button and you will then be presented with an authentication window. Enter the account name and password that has been set as the admin for this Mac. And then press the Log In button. You will then see another page stating that the information change is completed.
Now you can open an application and select to print and then check the appropriate paper source menu to see if cassette 2 is the default.