Considering that you have a supported CPU with VT enabled, you may have a look at the guest configuration file (.vmx) and make sure theses value are correct :
guestOS = "darwin-64" ich7m.present = "TRUE" smc.present = "FALSE" keyboard.vusb.enable = "TRUE" mouse.vusb.enable = "TRUE" monitor.virtual_exec = "hardware" monitor.virtual_mmu = "software"