Can't uncheck mute mac OS 10.8 book pro

Question

this has happened on the first awaking from sleep after installing 10.8
the f 10 key that mutes and unmutes sound has become stuck in the muted condition hitting it just shows the large sound level icon with the diagonal line through it but greyed out hitting the f12 key removes the large diagonal slash and shows full volume but greyed out and the small circle with diagonal slash is seen at the bottom centre of these large soundlevel control icons
the control in the menu bar is also greyed out and can not be adjusted from its bottom position.
the sound system preference shows out put volume at full but the the mute box is checked and grey and can not be unchecked.
sound was working after the install as I was playing with the improved text to speach voices...
the problem cropped up after awaking from sleep
all other functions seem to be OK
anything else I should try? ( I did a search here and found reports going back to 2006 here but they seem to centre on faulty headphone jacks and I have never used anything but the builtin speakers on this MBP)
Hardware Overview:
  Model Name:          MacBook Pro 15" mid 2009
  Model Identifier:          MacBookPro5,3
  Processor Name:          Intel Core 2 Duo
  Processor Speed:          2.8 GHz
  Number of Processors:          1
  Total Number of Cores:          2
  L2 Cache:          6 MB
  Memory:          4 GB
  Bus Speed:          1.07 GHz
  Boot ROM Version:          MBP53.00AC.B03
  SMC Version (system):          1.48f2
System Software Overview:
  System Version:          OS X 10.8 (12A269)
  Kernel Version:          Darwin 12.0.0
  Boot Volume:          Macintosh HD

Answer 1

ok as found elsewhere in these forums this is fixed by a full shutdown
power off and a fresh power on start
a restart selection from the apple menu did not work to fix it if it happens again after waking from sleep mode I will update this thread