When you change the brightness or volume though, do you also get the onscreen display to tell you the levels, or does it just change the settings without telling you more (and do you remember if it did before?) ?
Anyway, it sounds like you have one of the G73 models from your flashing battery light post, and you may want to tell us the exact model if necessary, but if you haven't installed the "ATKACPI driver and hotkey-related utilities" from the 'utilities' section of the ASUS download site (search by your G73 model to find the correct downloads)
http://www.service.asus.com/#!downloads/c1wax use it to see the onscreen display for the brightness and volume.
I haven't worked with the G73 too much and don't have one around to check, so you may want to wait for more replies, but your turbo button may not work with only the ATK driver installed and I'm guessing the turbo button settings are related to the Power4Gear Hybrid Utility which you may want to get too if necessary from the 'utilities' section.
Well, hope this gets you going in the right direction, or you can get some better suggestions.