the most direct way is
1. Open JAWS utilities on the JAWS screen
2. Arrow all the way down to 'explore my settings"
3. Open personalized settings.
4. Navigate to the file that has the same name as your spread sheet, with the extension .jsi and delete it.
that will remove all the JAWS settings for the particular spreadsheet and you can start over.
I strongly prefer to use the Excel bookmark feature for row and column titles.
With your cursor at the beginning of the row or column header (or the intersection of both)
1. Press the application key.
2. arrow up two or three times to "define name dot-dot-dot" and press enter. JAWS will speak the contents of the cell you are on, but just ignore him.
3. If you want row titles only, type the word "rowtitle".
If you want only column titles type "columntitle".
If you want both row and column titles, type "title'.
4. Press enter.
These entries are in the bookmark manager, which you reach with alt-m, then n., so they can be easily deleted.