Update CS4 to 4.1. This update wil give you a still directly to hard drive. Look under Export/Media, then in the export settings under format dropdown menu you select your type of still.
Have you got the lastest update (4.1) installed?
When using projects from an older version it is best to import them into CS4 instead of opening them with CS4. Sometimes these projects can give issues. Have you tried making a new track matte and does that work for you?
You tried to deinterlace, but you are not sure?
Its been along time since I used 6.5 but in the export setting one of the last window there is a checkbox for deintelacing. Did you check that one?