I feel like a bit of a duffer about this as I know that I have had Processing working before, however...

I opened Processing today after a long time since last using it and I cannot type anything into the Text Editor window.  

My Macbook is making a default 'cannot type here' blip-noise when I try and type into the Text Editor and the BG of the text editor window is blue not white as I would expect.  

I can create new sketches but it is still the same when I try and type.  I have restarted, uninstalled and re-installed Processing.  I have also deleted the preferences file from my library and restarted Processing.

I can open code examples (white BG shows then in the Text Editor) but I cannot edit the examples or even press return in the Text Editor window without my Mac making the 'can't type here' noise and refusing to allow me to add code.

Any ideas what I might be doing wrong?

thanks in advance.