I somehow wrote a really long post to say a few simple points. I had the same problem. I fixed it by reinstalling the img.
I'd been dealing with the same issues for about 5 hours or more. In the end I got it to work and it's the same solution that most people would give. I will post the situation incase others run across. The solution was to reinstall the image on the usb drive. That being said, I tried to install this thing so many ways, each time trying with multiple usb drives, all to no avail. I'm not 100% sure what I did differently in the end that solved to problem, but I have some ideas. What seemed like the major steps towards success were, (I was using Disk Utility in OS X by this point) Click options and select Master Boot Record, add a new single partition from the drop down to delete any old ones, and MAKE SURE that it is FAT aka MSDOS (I think this is where it failed one of the times that I thought I was doing a complete refresh of the USB; some random USB documentation said factory status use VFAT for the partition, and it didn't work for me. I was trying to start like I had a new drive. Just before this failed step I had wiped the drive with zeroes using dd, again trying to get to as close to factory as I could. I'm not sure if it helped since I was borderline about to give up at this point, so I didn't feel like waiting for Disk Utility to do a secure erase, but I did do a simple erase on the partition and the drive itself. Not sure if there is a difference but that's what I did. I also randomly decided to do a repair disk on the drive at the point. Nothing seemed to work so I figured what the hell. I went back to the original method of installing using dd on the image to the usb. Sure enough after probably the 50th time, it worked. I didn't have FreeNas installed before I started this though. I tried about a hundred different bios settings, since it mentions an xcci issue from error 19 in the documentation. Before getting it to work in the most basic way I had tried deleting and reinstalling in linux, mac, windows, with new images and checksums confirmed, tried different tools for installing the image, I took every other HD out of my system, I tried many of these steps each with 3 different USB drives. I think it only works in legacy boot mode using the method of dding the image to a usb. Once booting in legacy mode I would get the same errors you have, namely that the primary got table was corrupt (seemingly whether I did a fresh install using mbr) and mounting from us:/dev/ufs/FreeNASSs1a failed with error 19. I always got those same errors during the install. I used the 9.2.1.8 .img release.
In hindsight, I think something I may have been doing was not strictly using the mbr boot record. I think I was trying mbr or gpt, somewhat back and forth, combined with the MSDOS partition. I think since FAT and mbr are both kind of called msdos I may have not been as strict. After a lot of trial and error it was still failing using both mbr and FAT so I think there was more to it.
Helpful tips for others without reading. No guarantees:
Wipe at least the first few hundred MB with 0's before trying on an old drive, esp one with gpt. Doing this didn't directly solve the problem for me but I got it to work just after so it may have had some impact. (dd if=/dev/zeros of=/dev/sdb bs=2048)
Use MBR and then FAT on a single partition (like doc says), even though you are writing over it with dd it is somehow still important.
You can try repairing the disk before doing dd, I have no idea if it was part of the solution or not but it happened.
Obviously dd to the device not partition using this method.
Checksum image, I went back and checked mine later, but if had happened to be as simple as that and I wasted this much time I would not have been happy.
