Thank you for your post, and I apologize for the late reply.
If you cannot open the sample file, then perhaps the application is damaged. I would remove FileMaker Go from your iPod touch and reboot your iPod touch (to clear out any possible memory conflicts). Next, connect your iPod touch to your Mac, launch iTunes, and move over a fresh copy of FileMaker Go. Once the fresh copy is installed, launch FileMaker Go. If this still fails, then try downloading a new copy from iTunes. iTunes will see that you purchased the product, so a new one will be transferred without charge. Then, move over FileMaker Go to your iPod touch and launch FileMaker Go again.
If you have already found a solution, please post here so others can benefit.