When you 'lost' the control panel, it was probably replaced by three lines along the bottom of the screen (for health, mana and stamina). That is a feature; you can right click on the menu / lines to toggle back and forth.
I don't think Glide has been updated in awhile, which may be why Direct3D may (mostly) work better. Also, the game was designed for DirectX, since relatively few people have Voodoo cards.
If you check the readme file in the Divinity start menu folder, it lists a couple graphics problems that can be solved by checking 'Use AlphaBit'. Apparently is an alternate (I assume slower but more compatible) method to (at least) do color keying and fog.
