Dear Mr. Vassilopoulos (fellow Greek, I suppose)
Although replied at the end of the thread's queue, I found it prompt to reply directly to you at the thread's beginning:
At least in my case, this was the cause:
As it has shown up it has nothing to do with a proxy server.
It has to do with packages releases from DNN itself, - containing the content of the splash screen, upon a very new platform upgrade, like the 7.3.2 one.
So, since 7.3.2 was very recent, these packages could not have been propagated to all ISP servers.
Refer to:
https://dnntracker.atlassian.net/browse/DNN-5019