I had the exact same problem, PC PSD files creates in Photoshop CS5.5 wouldn’t come into FCP7 as layered. I finally fixes this when I found Photoshop 5.5 for Mac (I had a CS1 on the mac), installed it, then reserved all the PC PSDs and then they finally imported correctly as layered. For some reason, using the EXACT same version of PS (albeit one for Mac not PC) did the trick. Good luck.