Dear all,

Thank you so much for all of the suggestions.  Just to let you know by
re-installing the back-up it appears to have taken the problem away.  I have
noticed in the past however that these problems tend to re-occur.  I am
dreading the replacement of the source filament as last time there was a
short in the source and only by using a multimeter attached to the back and
gently inserting the source determining whether it was grounded or not.  
I so much appreciate all these responses and I am sure it helps others with
similar problems.  Cheers! Les