The original problem of not being able to download your LabVIEW code could be due to an unconstrained loop in your code. An easy check is to test solely with unaltered default framework after your next successful reimaging.
Download a fresh default project, then download it again to see if that works right or gives you problems.
If the default code works without your modified code ever getting in the way, then it's probably your code that's sucking up all the CPU cycles and there are easy ways to further test for that.
You probably know all this, but I'll just repeat it.
The procedure to clear and reimage using Safe Mode is to
- Flip the Safe Mode switch on & cycle the power
- Use the cRIO Imaging Tool (you'll get a warning that it cannot be reimaged, but proceed anyway)
- Flip the Safe Mode switch off & cycle the power
- Use the cRIO Imaging Tool again to download v27
- Cycle the power and watch the cRIO yellow status LED. It should only come on once.
- Build and Run as startup an unchanged default project
Then, as a follow up:
- Test the project
- Confirm that you can download again