Comfort Update does not work any more

Hello,
since a few versions the Comfort Update does not work any longer.
Error: 0 could not connect to host "update.limesurvey.org" (picture_1).
The next screen tells that the Update-Server is busy and I should try it some 10 minutes later. (picture_2)
We are definitly NOT behind a proxy and we can ping to the update-servers with no problems.
When I switch on the PHP-Error-Log I get the log as shown in PHP notice.html.
Has anybody a idea?
Best regardes

Notice: the file PHP notice.txt is a html-file.