The problem disappeared after a few hours. I will post again if it recurs. For what they're worth, here are the answers:
Desktop Support wrote:
Do you have any error message?
If I remember correctly, the messages might have varied between the different listed situations, but they always involved the timeout exception mentioned in original post.
Desktop Support wrote:
Are you sure you are using the latest .jnlp from the website?
If it happens again I will try getting the jnlp from the website and see if it makes a difference.
Desktop Support wrote:
Have you cleaned your JAVA cash?
No.