How can I tell if my International Galaxy S3 is suffering from Sudden Death Syndrome? If it is, how can I fix it?
Do this:


Type *#0011# on your dialer to go into Service Mode. 
From there, go to Settings by pressing the left hard key
Navigate to wifi and turn off power setting mode.


This solved the problem for me. 

However if you turn your phone off and again, the procedure will have to be repeated on each restart as its temporary.