Photoshop CS6 - Unavailable file formats

Question

Hi everyone!
I just downloaded a trial version of Photoshop CS6 and noticed that I had an extremely reduced choice of file extensions at the moment I wanted to save my work. In fact, I wanted to save it in .tga, but the option disappeared from the list. The PSD file I want to save only has 4 layers, 3 of which use an alpha channel; the 4th being a plain black background.
And the weirdest thing is that when I create a new, empty file, I can save it as a .tga image, along with a lot of other extensions that disappeared for the other image. Like, I can't even save my first pic in BMP. I only can use PNG, JPG, CIN, IFF, TIFF, and 2 or 3 others. 
So, what's wrong with Photoshop?
Oh and by the way, it's the x64 version. But it does the same thing with the x32 one. I tried already.

Answer 1

Kyphros wrote:
…Photoshop never did that in the previous versions though. Seems strange to me.
Kyphros,
I just tried saving a 16-bit image in Targa format, and neither CS4 nor CS5 would let me do it.
However, the specs for the file format say "…The format can store image data with 8, 15, 16, 24, or 32 bits of precision per pixel[1] – the maximum 24 bits of RGB and an extra 8-bit alpha channel" which is kind of confusing.  ( http://en.wikipedia.org/wiki/Truevision_TGA )