Like I said this has nothing to do with latest WinUAE 1.2.0 just because it works here with AmiKit.
Anyway, the problem is that IPrefs sometimes crashes during the startup and the message about the crash is displayed behind the boot picture. So it looks like the AmiKit is still booting. Try to press Esc to quit the boot screen and you would be able to see what is happening behind the picture.
But like you said, you've already passed DOpus request window that means you've also survived the IPrefs crash :) In that case, if the cat boot screen is displayed again after you press the "Run" button in DOpus request window, press the Esc button to quit the boot picture. It's possible that some kind of requester is blocking the boot process and you do not know about it because the boot picture is in front of it.
Another reason could be that ShowAmiga96_Close program is missing in AmiKit:WBStartup drawer. This program closes boot screen at the end of the boot process.
Well, the best solution for you would be to disable cat-boot screen completely, edit s:startup-sequence and disable this line:
by putting ; in front of it, so it will look like this:
To do this, boot without a startup sequence and type:
When you save the changes, please ignore the "can not delete file..." message, your new startup-sequence will be saved anyway.