Angel_wing...when you do a *#0000#, what is the number in brackets after the N73?
The reason why you are not getting the upgrade is because of your phone localization setting.
Mine is 02, which is the Euro_2. It can be that Nokia has not released the firmware for your localization that your phone is set to.
The easiest way to get around that is to change the Product ID of your phone, which will tell NSU that your phone is a different localization and then it will upgrade it. Of coarse if your phone has a APAC firmware now and you wan to keep the APAC firwmware, then changing the ID won't help you.
Normally, Nokia will release Euro flashes first before the APAC ones.