Something is very wrong
Check if the singlepage-mode parameter is set up correctly in the headers, as explained here.
Formulas are mixed up
Do you have to singlepage scribble files in the same directory? See Avoiding Conflicts
Execution of the command “scribble ...” freezes
If your talk has many formulas, and this is the first time you are
executing the scribble command, you may need to wait 1 min or so...
But sometimes it, really, freezes.
This may happen on slow machines. Do the following: