I have a number of textfields in the project and have set requestFocus() on each so that it tabs to the next one,
I have no idea what this means. Nowhere in your code to you requestFocus(). By the way
you should be using
requestFocusInWindow().
In any case tabbing happens automatically. You don't do anything special to enable this. Basically it goes left to right and top to bottom.
i then have a combobox again...
Well in the code posted when you select an item from the combo box you make it invisible, which means focus needs to go somewhere. So I'm guessing Swing determines it needs to go to the text area. Use the requestFocusInWindow() method to have focus go where you want.
If you need more help then post a proper
SSCCE that demonstrates the problem.