I have several stardock accounts going back 10 years+.  I purchased the digital download of the game, got my key in the email address I use today, and tried to register it to a stardock account that is old and I dont have the email address to.

1. Registration succeeds

2. download succeeds

3. install succeeds

4. go to click on Internet play, enter the same username and password i entered to download the game just now, and it tells me its wrong. 

5. Try another impulse account, same problem

6. finally created a NEW impulse account, tied to my current email address, verified it, and re-registered the game.

7. logged in first try!

Was a pain in the ass, so hopefully others will benefit from the suckage that has been using impulse.