I am having the same problem with Sketchup Make 15.3.329 Mac, which says it is current as of 3/15/15.
I installed SketchUp STL, downloaded from here: Extension | SketchUp Extension Warehouse
My .stl file is a 3D scan of my head & shoulders. It runs about 23 MB. Unless Makerbot is selling orangutans, my file surely is an .stl file, not an orangutan with .stl tacked onto the filename.
When I try to import the file to SketchUp, it hangs. Reproducible error.
Any ideas? Thanks…