That dialog box indicates that LabVIEW is searching for a specific file (in your case, "NIMS_[I32,I32]=size(GM).vi" ).
If it doesn't find it, it may be that you're missing some required toolkit (this is less likely given that you can open things depending on order).
If waiting doesn't work (this may take some time, ~30s - 2 mins?) then you can try clicking Ignore. This will load the project with a missing file, but may allow you to try and change some aspects of the problem.
A second dialog box may pop up when it fails to find the file (during loading) asking you to navigate to the file and select it. You can click cancel for this dialog and then Ignore, if you don't know where the file is...
When you open the first VI, it probably loads from a path relative to that VI, which allows the project to then use the copy found "in-memory". Is there a file with that name near the subVI you're opening?
I suspect you may have a project you've copied from another computer, or downloaded from a colleague/friend/associate etc. Is that close to correct?