[mythtvnz] Myth gives up on a recording

[Noel & Di]

The last few nights a program we have been watching (about 1/2 hour 
after it started recording)  has ended abruptly.  The schedule is red & 
the status says the tuner is still active, but the record finish counter 
on the screen isn't incrementing.  The recording can be watched up to 
that finish time shown.  This has started spontaneously happening.  
LUCKILY for me we'd nearly caught up on the live broadcast of Coro, so a 
quick change to a FTA box we have saved my bacon - only missed 3 mins of 
program, but the WAF crashed.
Has anyone got similar issues? is one of my cards dying do you think?