I've had exactly the same problem, but..
I just bought ytk today..installed it and was working fine in chat etc... but then I needed to reboot my laptop, and on reboot I got the dllreg error. Yahoo wouldn't load and guess what the lil ytk icon is unresponsive. It won't let me right click on it to do anything. I opened up task manager and it didn't show there so I couldn't close it that way. Only way to get the icon off the running programs box was to reboot my computer, which in turn caused it to load up again, error again, and freeze itself and yahoo again.

So I deleted ytk completely off my system, rebooted, got rid of the folder, tried to re-install but it wouldn't ask me for my reg key again even though I'd deleted everything and had to go back to your site and re-download ytk again. Should it not have asked me for my key again?

Frustrated and cornfizzled
Jen

ps: I also tried downloading it from the link in the email first..a couple of times. It loaded up fine...then I'd get the error again when I tried to log in. Helppppp lol