Bullet image file not added to Webhelp folder

I just updated an older project to my current RoboHelp 8 version. The gif file I use for a bullet image is not being added to the Webhelp folder when I generate Webhelp.

The image is listed correctly in the css (list-style: url("Bullet 3.gif")) and in the RoboHelp list style (LI+ list style: url("Bullet 3.gif"). It also appears to have been added to the project's images when I look in the Images list in the Project Manager pod.

The bullet appears correctly on the Design page and when I click the eyeglasses preview icon.

I have tried re-adding the bullet to the images on the Image dialog box and re-adding it to the style by browsing for it in the Styles dialog box.

I suspect there may have been a problem in the previous version when the image was added not from the project folder but from a different folder, but the file is now in the project folder and I have browsed to it in that location everywhere I can think of in order to convince Robohelp of the file's current location.

Does anyone know how I can get RoboHelp to add this file to the Webhelp folder?

Thanks,

John