For better support of SDXC cards:-
http://www.pentax.jp/japan/support/download/digital/645d_s.html
http://www.pentax.jp/japan/support/download/digital/k5_s.html
http://www.pentax.jp/japan/support/download/digital/kr_s.html
http://www.pentax.jp/japan/support/download/digital/kx_s.html
http://www.pentax.jp/japan/support/download/digital/k7_s.html
Update (3-6):-
It seems that there is a bug in this batch of firmware update that the user is required to do a complete reset to the camera after flashing the new firmware, otherwise strange things would happen! Just see two of the latest user reports on the issue:-
http://forums.dpreview.com/forums/readflat.asp?forum=1036&thread=40820302
http://forums.dpreview.com/forums/readflat.asp?forum=1036&message=40771664
[First Post: March 1, 2012; Last Edited: March 6, 2012]