I know that a red line below the work area in the timeline panel means that rendering preview files is necessary before playback, and that a green line means that rendering preview files is completed.
Can someone fill me in as to what a yellow line means. Clips seem to playback without difficulty when the line is yellow and the sequence imports into Adobe Encore without difficulty.
Yellow line means the clips dont match the project preset but they will preview in real time.
As per Curt's answer, you might want to compare your Project/Sequence Presets, and the specs. of those Assets. They should match. If you need help getting the exact specs. of those files, Properties Panel should help you. If not, G-Spot will likely give you all you need.