error :line 1, column 2: XML parsing error: <unknown>:1:2: xml ......

line 1, column 2: XML parsing error: <unknown>:1:2: xml declaration not at start of external entity [help]

  <?xml version="1.0" encoding="ISO-8859-1" ?> I have validated for months my simple rss page without any problem, but since 3 days a get always the followingmessage:line 1, column 2: XML parsing error: <unknown>:1:2: xml .I have tested with you w3 validator  other rss document on the web,and I have discovered that almost all the rss documents on the webhave got the same problem  and the same answer: line 1, column 2: XML parsing error: <unknown>:1:2: xml .What is the real problem? How can I solve it?Regards virginio sparavigna