HA! yes dude Im going through the same thing right now. Just bought a key not too long ago. Tried activating it and got "key is invalid" message. Ive sent GMG an email hopefully they respond soon I wanna get this preloaded.
Yea, they didn't reply to me yet. Ive been trying to input this code for the last hour, with no luck. If what they say is true about Steam being slow, then it might work tomorrow. so Ill just give it another shot tomorrow. sucks..