Norton flagging a threat on valid software

Hi I am new to the forum and hoping that someone can help with my issue. I recently bought a program from Appletree called YTD Pro, it allows me to download video's from Youtube.  I had difficulty in downloading it as Norton kept flagging it as a threat. I resolved this by turning off my security program temporarily and was able to successfully complete the download.

Now I am getting repeated messages to say there is an unresolved issue on my computer, Norton does not feel they have a problem and said it is a genuine threat. Appletree says its s false threat and Norton's problem.  Can anyone help, short of removing Norton and moving to another security program     Much Appreciated     Alex