The recent Sony HVR-Z7U and HVR-270U cameras both use CompactFlash cards to record HD video. Unfortunately, this technology is currently limited to an invidivual 4GB of storage, as FreshDV notes:

One of the issues with the CompactFlash media workflow introduced with the new Sony HVR-Z7U and HVR-S270U camcorders is the fact that CF cards are formatted in FAT32, therefore they have a 4GB filesize limitation (that’s about 20 minutes of video). Much like Panasonic’s method of spanning P2 cards, these new HDV camcorders simply split the recorded M2T clips at 4GB for rejoining later.

Thankfully, Sony has released a Final Cut Pro plugin that will allow editors to still use Log and Transfer functions. This alleviates the issue of split media by automatically joining separated segments. Grab the plugin here.