In 2012 things work great, but in older versions for what ever reason Revit's Spell Check function only checks what is in the current view. To spell check a project, each referenced view must be opened and spell checked.
Here is a tip on how you can spell check MOST, if not ALL, of an old Revit project.
1. Go to any view that has a text note.
2. Select the text note and right click.
3. Choose "Select All Instances..."
4. Then choose "In Entire Project..."
5. On the Ribbon, select "Spell Check"
This will spell check every note of that Text Type in the entire project.
Repeat the steps for any other Text Types in your project.
This will leave out text objects inside groups, families, etc... But, it is better than nothing at all.