Dear Todd,
unfortunatly, i have the same problem as you described in your post in february: Clips that have been visible using FCP 5.1.4 or P2 Log on a PB 10.4.2 are not visible with MACBOOK PRO 10.5.2 using P2 Content Manager. They appear white even if the preview window is giving a proper icon. Unfortunatly the software seems to change the clips or metadata. After trying to re-open them as done before with PB, they appear white there now too.
Too bad. Did u find a solution why they are shown white in P2 Content?
best,
andi