According to the Technical Requirements: The "_color" texture can be 24 or 32 bit. Use 32 if the alpha is needed for opacity So simply apply a 50% grey alpha (I'd go a bit lighter, 50% may still be too little) where you want it to be semi-transparent and save the diffuse color as a 32 bit.
use targas. if you have an alpha channel in any of your maps that you are using for transparency....save as 32 bit. actually, i just save everything as 32 bit.
It should work but I believe that you have to have 32 bit Python installed as well. Also keep in mind that 32 bit RAM limits will probably also be in place.
when i'm not looking at this bar frozen at 32%, i'm watching some dude lick glass. Edit: Bam, done decrypiting, hung at 32% then plowed though. Enjoy the game everyone!