DVD drive disables upon boot, Studio 1557

Hey guys!

I have a DELL Studio 1557 and have problems with the DVD drive.

Newest drivers were installed from official DELL driver support side:

DVD_TS-T633C 12.7mm Slotload8xDVDRW_vD800, A07_5.4.10

I am using Windows 7 x64 Ultimate as OS.

The problem is, that when I start my computer, Windows just does not recognice the DVD Drive (the BIOS actually does, also booting from DVD/CD is possible)

So if this is the case (not always!) I open the device manager and enable the drive, then it works like a charme.

So is there any Windows-specific setting which disables the DVD-drive?

EDIT: I've already tried to remove driver and install it again... same problem

Hopefully somebody has an idea, thanks in advance