Hey Guenter,
When wyUpdate downloads files it first tries the proxies on the system or ones you specified. If those proxies fail then it tries to directly download the file. So the problem is that wyUpdate is failing to connect to your proxy.
You say your proxy is password protected, and yet you're not passing a username or password. You must. Something like this:
wyUpdate.exe -proxy:"http://proxyserver:80/" -proxyp:"PASSWORD" -proxyu:"USERNAME"