ambiguous content model - yea or nay?

Question all,

I am getting an "ambiguous content model" error when validating an instance conforming to this schema:

<xsd:complexType>
     <xsd:sequence maxOccurs="unbounded">
          <xsd:element name="AvailabilityStartDate" type="AnyDateTimeNkType" minOccurs="0"/>
          <xsd:element name="AvailabilityEndDate" type="AnyDateTimeNkType" minOccurs="0"/>
     </xsd:sequence>
</xsd:complexType>

I only get the error from 1 of 5 parsers/tools that I validate against.  And only when validating the instance (the schema validates just fine with that same tool).

The more I looked at it, the more it seemed "technically" true but I wasn't sure.

(For the record, this is a bug fix - I plan on eliminating the maxOccurs attribute on the sequence.)

Curiously,

Paul Kiel
HR-XML Consortium