Issue in workspaces

I found something wrong with workspaces.
Exists only if you use programs that have many cards and open files/urls 
in the same app instance but in cards. If you open url, browser don't 
open next instance of app, but open new card.
In this way works firefox (with some settings), icedove and acroread 9.0.
To do this bug, follow my steps:
1. open firefox in workspace 2
2. go in workspace 1 and open xterm
Now, you have on wspl1 xterm, on wspl2, firefox
3. in xterm use command to open file or url.
4. you will see your app with your file/url, but getnev wspl gives you 1 
(not 2).
5. If you change workspace for next, and you return by prev, you 
discover that wspl1 and wspl2 have the same view. Even if you move by 
mouse your document, on the second workspace you have the same. 
Something like: you have two the same workspaces. Of cource, moving 
windows by next / prev solve it, but for first time user can't realize 
what's going on.

Instead of xterm you can use mc or whatever that gives you launch apps.
Application must have functionality that opens many documents in the 
same instance, like cards in firefox, or cards in acroread (it's new). I 
don't know other apps like this but I think they are.

Thank you for reading.
Marcin.