I don't know if this will help but on your Asus drivers CD there should be an option to install the Asus Probe utility.
Install this, then execute it, ususally from All Programs/Asus Utility. Click the icon that it places in the system tray (bottom right) and select the settings tab. Here you can set the threshold fan rpm values to anything you wish.
As I say I don't know if this will affect the BIOS message but it's worth doing if you haven't done so already. The default threshold on mine is 600rpm.
The reading you quote sounds more like a temperature (51f) but you can change that threshold too.