Bill,
I believe you are correct here. If the source clip is offline it appears red. The grey hash marks indicates the clip is pointing to in and out points that are unavailable in the source file. This can be for two reasons I can think of. One is if the clip was shortened in an external editor, like Audition. Sometimes you will see only half the clip with the hash marks in this case.
The other reason is a particularly problematic issue for me currently. I have an XML import from FCP and roughly half of the clips have the grey hash marks because the project file is either misinterpreting the framerate of the footage (most likely, I think) or the translation from XML is inaccurate. All the source files play fine in the source monitor as was mentioned in the previous post so i don't suspect a codec problem, but if you look for the in and out points of the selected clip they are often long after the video has ended.
The other odd thing, not sure if related, is that the audio gain in the clip efffects , which drives the yellow line, is set to -infinnity in each.
If anyone has any experience with this problem please share. I can manually slip all these clips to revael the proper portion of the clip but that will be a tedious process obviously. I would love a global answer to this problem.
Thanks in advance.
Chris