Edit can't be undone ù proceed anyway?

You won't be able to choose the Undo command to restore the current state after you perform this edit. This error has the following cause and solution:

• This typically occurs when an edit is simply too large to be saved.

  Try performing the edit in smaller increments.

For additional information, select the item in question and press F1 (in Windows) or HELP (on the Macintosh).