Why would certain filters (i.e. artistic, etc) be blocked on CS3 Photoshop?

I am running Mac Leopard and now when using Photoshop CS3 certain filters are blocked. I open an image and the filters are not listed. I only have about 5 listed [blur, sharpen, and about one or two others]. The more artistic filters such as postorize, artistic, sketch, texture, and brush strokes are not listed. I have the mode set at 8 bits/channel but still can't use specific filters. Is there anything I can do to access them?