This caused a lot of headaches but was finally solved this morning. Brainwave (and a nights sleep) needed to find the cause and it was so simple!
The case being that between my last successful access of the garden and yesterday the firewall protection of my modem had gone up to the highest level of protection (firmware update by ISP maybe, one is not always informed when these happen). Anyway, setting that level to low enabled the rsync service to the garden. Afterwards I set the protection level back to high, of course.
I hope that leaving this solution on the newsgroup will spare others the same headache.
Finally I wish to thank those who helped me search the culprit, especially Mojca who spent an hour with me on this case.
This used to give me the latest contextbeta:
Today I get this error
start download and iinstall of contextbeta
Is the garden down or have the sources been moved since my last access this June?