the monitor that i have it connected to right now is a Samsung Syncmaster 2443BW, which i believe is 1080@60Hz. The recommended refresh rates are 59Hz and 60Hz. If i un-select the option to show all refresh rates there aren't any additional refresh rates.
Ihaven't connected it to my TV yet, which is 24Hz capable, since i'm still having problems (bsod) with the windows installation.
Is there is any change you can test the other T.V? The refresh rate will depend on the TV/Monitor that you are connecting, in this case Samsung Syncmaster 2443BW will only show the refresh rate that is capable of handling.
ok, i tested it on my TV and it show all supported refresh rates, 23Hz included.
If you need further assistance let us know.