Interesting one, this!
If you ping the URL, it resolves to 80.82.115.66. However, if you load 80.82.115.66 into your browser, it arrives to a server default page, because the hosting company is using some mechanism to host multiple sites at one address (possibly host headers).
Now what seems to be happening with PPRuNe is that the link URL is tested in some way, perhaps as an anti-hijacking measure, and found to be "broken" - re-directed or malformed - so is then ** out.
It seems to me that one or other (or both) sites is mis-configured.
Bloody annoying!