I saw a post that had a similiar problem, so I did the following:
Opened a Command Prompt as Administrator and ran "slui.exe 3". Entered the product key I have and it tried to activate online, giving me the same error response "A problem occured when Windows tried to activate. Error Code 0xC004E002."
Then I ran "slui.exe 4" and chose Japan as my location, as I'd rather not be making long distance phone calls from my mobile.
Fortunately, they have a "press 2 for English", which I did, and after ignoring the "enter your code" message 4 times, I connected with a real person and she had me read off the ID, then gave me the activation code.
Entered that in the right places and all went well and it activated.