Thank-you so much for the replies and good wishes!

It's nice to know I'm not alone although it doesn't seem to be a common problem.

Like Kat and Satya I have had all the tests done and they can find nothing.

It reassures me to see that most of us here get there in the end, even though we don't get any answers.

Let me know if you find any-thing out Kat!

Shell X