OK that seems rather strange. Your recording devices shouldn't have mute checkboxes - they should be labelled Select and you choose which source you want to record from.
Go into the AC97 Audio configuration and look on the SPDIF out page. You seem to have Stereo Mix selected. Make sure that you select "Output Digital Only" or preferably "No output" if you don't have any digital speakers. On the Realtek HD Audio control panel these might be labelled something different.
Bottom line is, if you have set your SPDIF to "Output Digital and Analog" then annoyingly, the recording control is fixed to Stereo Mix and the sliders cannot be moved. Usually the first time you chose this option in the SPDIF page it should give you a popup warning you that the recording device will be fixed in Stereo mix, but of course the popup can be told to piss off for good, so its easy to overlook this small thing!
Your drivers are one step ahead by actually disabling the sliders in Recording control - for my drivers I get teased by having all the options in the Recording control panel left enabled but as soon as I try and change anything, they are all frozen together! As soon as I change the SPDIF output to "Output Digital Only" or "No output" then the sliders can be adjusted again!
Failing this, check any front panel audio connections - sounds farfeteched but a loose fitting HD Audio front panel connector could cause havoc with the UAJ sensors, and this could in turn give problems with the drivers.