The problem was that AmiKit checks for newer version of WinUAE on your system, and if found, this newer version is used instead of the internal one. So for example if you have installed new WinUAE 1.4.3 (using its installer) into C:\Program Files\WinUAE, the AmiKit checks this location and uses this executable instead of the one located in C:\Program Files\AmiKit\WinUAE\ folder.
Unfortunatelly, the WinUAE 1.4.3 has a bug in path system it could not found the AmiKit location (ROM and HDD) even though it was specified. This resulted into the violet kickstart screen as you described.
It seems this issue is fixed in the latest beta version of WinUAE. Please download it (WinUAE 1.4.4 beta 1
) and copy the executable into your installed WinUAE location, eg. C:\Program Files\WinUAE\