The latest firmware upgrade version 1.04 is now available officially from Sony Asia Pacific. I have downloaded firmware in the past for my A900 from this source so I can vouch for it's authenticity. It's just that they always get it before the UK or US!
The new firmware expands the number of lenses that permit use of fine focus adjustments (including the Vario-Sonnar T 16-80) and a few other nice goodies!
Just click on downloads and follow the instructions for your computer platform.