I, too, have this problem, but on my laptop with LM 14 64-bit MATE; every time I try, the mouse and keyboard freeze up. The numbers lock light stays on, trying ctrl+alt+del doesn't work, caps lock won't turn on... nothing.
As you said, my keyboard/mouse work fine in Windows 7. If it were a hardware issue, then it wouldn't work in Windows 7 (and since I'm typing this in my Windows 7 installation on the same laptop I'm trying to install LM on, we can see this isn't the case).
Some added info for me: I DO have LM 13 64-bit installed, but this issue still pops up randomly on the login screen. The keyboard works fine on grub, and I can turn the num lock on and off, but then somewhere in the boot up, it won't do it anymore. When the login screen pops up, mouse and keyboard aren't working, so I have to do a hard reboot and try again. Sometimes, it works on the first try, sometimes it takes multiple tries.
This isn't an isolated problem, either; others here on this forum seem to have the exact same problem, and haven't had any luck even with switching out keyboards and mice. MATE, Cinnamon, 64-bit, 32-bit... all seem affected by this.
Anyone have any ideas?