Have you tested the link yourself as described above? You would need to reactivate the link since it has been expired, or you can send the buyer a new one, but you have the ability to test the same link yourself to verify whether or not it is working should a buyer have problems.
Yes, I tested it and it downloaded as it should.
That doesn't mean that your buyer isn't having a hard time, but it will demonstrate that the problem doesn't lie with the link itself but with something on the buyer's end of the connection that is out of your control or ours. It is quite possible for an individual to have a poor internet connection to some sites and servers and not others, that's just the nature of the internet. Trying different connections (such as work versus home) is a good way around the problem, so is trying at different times of day.
It get more interesting. I sent my customer a "free" download link to one of the four 300MB files. The exact same link provided in the e-junkie HTML page with four links. My customer had no problem downloading that file. What's different???
As for the cursor issue, "forum software" doesn't provide cursors, that would be something related to your browser or operating system itself.
I've run a lot of forum software over the last 10-years, perhaps 10,000 posts. Never had a missing cursor, intermittent or otherwise. This forum software is totally lacking in basic features I've come to expect. Like a simple post review. There are many great free forum apps out there, why did e-junkie have to invent this buggy and featureless tool?