I've found two problems that cause this error:
* Hidden VIs.
* VIs from very old versions of LabVIEW.
Let's say you have a VI loaded and you do "Save as" or "Save for previous version", then select to save everything to a new tree. Your VI may show a white run arrow even though it can't be saved.
This is because LabVIEW is too clever. When you disable a section LabVIEW will remove it from the hierachy diagram. It also won't tell you if it contains SubVIs that LabVIEW can't find. If there are any SubVIs that LabVIEW can't locate then saving to a new tree will fail. So, you could have a hidden section deep in your hierachy that points to a single missing VI, that will break the save. Also, the disabled section could contain a VI that works, but it's for a very old version of LabVIEW that modern LabVIEW can't deal with. Again, if the VI is in a disabled section LabVIEW won't complain, but it won't save new trees either.
This is what you have to do:
* Find all the disabled sections. A simple way to do this is using the hierachy diagram. Let's say your main VI has 4 SubVIs which call many SubVIs. Take each of those 4 one-at-a-time and try saving it as a new tree. One or more of them will fail, that means there's a disabled section there.
* Once you have found the disabled sections then:
** Delete the section if it's not needed, or:
** 1. Look for missing SubVIs, the big "?".
** 2. Look for VIs from very old LabVIEW versions. You can do this by copying the contents of the disabled portion to a new VI and seeing if the run-arrow is broken.
