It's an old Logitech WingMan. With USB interface. I also have another one older (with the 15 PIN joystick interface) but this last one never worked on my PC with Seven. It was used to work fine with my previous machine with XP installed.
I don't think I'm the only man on earth that is using old hardware to play MAME games. I know you're aware that a lot of people with cabs and/or old PCs will be cut out if Direct Input 7 support will be dropped. I also recall some MAME Testers entries about this.
I posted here the bug because it was not related to my joypad. Now it's fixed. What else? I'll not make Moogly happy, sorry.