semi-transparent textures appear opaque

What textures ?

Please attach a screenshot.

With a custom Texture Pack, I've modified the glass block.

What is semi-transparent ? Alpha channel ?
How does this look in vanilla 1.4.7 ?

Yes, it's Alpha Channel

Does vanilla minecraft support alpha blending on blocks especially in glass panes / blocks ?
I do rememeber that this was added a few versions ago in MCPatcher.

Again the question: How does this look in vanilla 1.4.7 ?

Excuse me, I don't know it. In vanilla 1.4.7, it's the same. Thank's, you can close this report.

Thanks for the feedback, ticket resolved.