instead transparent i see now black color, but reflection on the floor shows that
legs of one guy are including transparency

Does it show correctly without shaders on? Could be a hardware/driver thing, could be a transparency bug in the client, could be a combination of hardware + client causing it.

Yes, without shaders transparency works. I upgraded gpu from geforce 9500gt to geforce gt 630.

Hmmm, they should be working perfectly. So long as you're using a current non-beta driver everything should look right.

Have a poke through the Nvidia control panel & give the default settings a jab in the ribs. Specifically the quality settings, and anything for GL.

I'm experiencing the same problem.
I had thought that shaders had worked with transparency before, so I went and checked in some older versions [i'm currently using 4.8]. I went and looked in 4.41 to see if transparency had anything to do with the version, and the transparency is working with shaders on that older version, but in 4.7 onwards, the shaders produce that black stuff. I just wanted to add some information that may hopefully bring some light on this issue, and what in the updates might be causing it. I changed no settings between my clients, they have the same settings enabled on all 3

Hmmm, might be something that's been changed in the render to make the game work on shitty Intel stuff caused the break? Could be any number of things.

I'll prod the devs about it.