Ive had the same problem first. Ive tried to install FreeNAS on my CF-Card by using a programm called Roadkil`s Disk Image (and another programm) on my Win7-PC. I tried it x-times, but it wont run. I solved the problem by installing FreeNAS on the NAS-System from the Install-CD. Now FreeNAS runs fine!
Hope that helps you too!