First, empty your disk cache (blue line should go away). Second, turn off all effects, Third Purge all caches (Edit>Purge>All), then try a ram preview again.
If you still see the random green then it's probably the codec used for the video. I'm not familiar with the camera but I assume that the format is AVCHD or MPEG2. Both these formats could become easily corrupted or the decoding could fall apart if you have some other third party plug-ins installed. Check your System Preferences and see if there are any other video codecs installed.
As a last resort, load the clip into Premiere Pro and send it to the encoder and render out a qicktime with jpeg compression. If the transcoded footage works fine in AE then you'll know that it was a codec problem.
One last thing, Still don't know what version of AE, if AE is up to date, or what the properties of your movie are. You can find those properties by opening the movie info window in the QuickTime player or by simply clicking on the footage in your Project panel and looking at the top just to the right of the preview thumbnail.