I sometimes get an exception when saving a zip file, using ZipFile.Save().
When working with 126.96.36.199 it's "The method or operation is not implemented".
When working with 188.8.131.52 it's "Specified method is not supported".
It's not always happening. I couldn't point out the exact scenario, but I saw that the first access to the save() function works ok, but repeated calls will most likely fail as described above.
Any idea what happens here?