Some of my older Vegas projects have Particle Illusion clips rendered using HuffyUV codec. Now, on Windows 7 64bit, I can't install HuffyUV so Vegas can't see the older projects.
> There's a huffyuv64 version here (try at your own risk -- I know nothing about it):
If that doesn't work, use the 32-bit version of Vegas Pro which does use Huffyuv and convert them to Lagarith which definitely has a 64-bit codec that works. Both codecs are lossless.
Largarith definitely does work well with PI.
But as for HuffYUV? I have installed both 32bit and 64 and they don't offer themselves inside Particle Illusion.