Now I have to mention that this hack isn't required anymore in Mint 13. There's a new mintmenu-keybinder package which seems to include the whole old deskbar-applet package contents, and so the global menu hotkey is working again.
Update: LMDE now has this package too. Mint 12 hasn't received it yet (and maybe it never will).
OK, thanks for this. This is just to inform you all guys that this one works beautifully in Mint 13 MATE (actually Cinnamon with mintmeta-mate installed). I've already mapped Super_L only for the purpose to open the advanced mint menu (instead of ctrl+super_L). The interesting thing is that I'm not able to add any of the super keys in any keyboard shortcut combination in mate-keybinding-properties, but I guess this is for story. It is like my super keys are not working at all (which is not the case after mintmenu-keybinder installation).