I've been trying to resolve this problem through Technical Support by I appear to be dealing with automated responses (no direct answers to questions). When I output files using AVCHD (regardless of settings - I've used both Hardware and Software rendering options, I've cleared my Proxy files, and I've experimented with all FPS options). I'm using Windows 7 64bit, RAM is 8gb, and a Radeon 6950 video card with 1gb of VRAM. My CPU is an i7 2600 (3.4ghz). There IS a suggested solution posted for this problem (enable Smart Proxy), but it only appears to be available with NXT 5. I'm sort of committed to Roxio (I have about 20 very large files that would be extremely time consuming to recreate using another software) so I'm getting pretty desperate. At the moment I'm considering just upgrading to NXT 5, but it's a risk as I can't be certain that this will necessarily resolve my problem. As I mentioned before, Technical Support is simply sending me generic fixes and won't respond to direct questions.
Please help me, I'm desperate!