The thing with MapCounties has been fixed now. We updated the US polygons 1-2 days ago and the new ones used a bit too much memory and caused an error in the server end. If it was very very close to the limit it could have been that it worked sometimes/"randomly".
Long-term we will make a better solution, but for now we just allow more memory usage.
The second issue is unrelated to the first. But the links work just fine here (Ubuntu+Chrome). Generally I would say "try shift-reload", but if you have tried that one as well in multiple browsers it doesn't make sense. The maps are a bit stupid and therefore requires a bit too much resources of the client computer. It could potentially be that the web browser doesn't really like it when too many geocaches are shown. As a test I would add some filter to only show higher rated ones, which should reduce the number of geocaches a lot, to see if that works. Your link showed almost 3000 of them. However, a modern computer should be able to handle 5000. But this might also depend on other facts like corrected coordinates and such.