Thanks all for the suggestions. It was a problem around not being able to save changes (not just wireless). I reloaded V1.21 firmware but this made no difference. I tried reloading an old saved configuration but this made no difference. Finally I restored factory defaults and rebuilt the config from scratch. All is working fine again.
I suspect, from reading earlier posts at this forum, others have gone through this process and it did not work for them. But it may help others.