What configuration changes have been made to the pix? Did you recently apply a crypto map? If you did and its not configured correctly, the pix will be locked up. Check for a applied crypto map, remove it. Do a wr t, not a show config. Things will return to normal after removing, hopefully. On the other hand, if you have a network down situation, i'd suggest you call tac, if what I mentioned isn't there. Hopefully you have a some type of contract on the pix. Otherwise post your configuration here so we can take a look at it. Again, make sure its a "write terminal".
Kurtis Durrett