"minOccurs", "maxOccurs" attribute not allowed error

[Sy...@aol.com]

Hi,

I am trying to use xmlbeans to generate JavaClass.
I got this error:
[xmlbean] anguage.xsd:405: error: Attribute not allowed: minOccurs in element 
choice@http://www.w3.org/2001/XMLSchema
  [xmlbean] language.xsd:405: error: Attribute not allowed: maxOccurs in 
element choice@http://www.w3.org/2001/XMLSchema
 
Here is the part of the schema causing  the problem:
 <group name="contentControlGroup">
        <choice minOccurs="0" maxOccurs="unbounded">
            <group ref="smil20lang:switchGroup"/>
            <group ref="smil20lang:prefetchGroup"/>
        </choice>
    </group>

There are other part in the same schema which uses "minOccurs", "maxOccurs" 
too, but it works, only the above case does not work.
this case works!
  <choice minOccurs="0" maxOccurs="unbounded">
                    <any namespace="##other" processContents="lax"/>
                </choice>

Can someone please tell me how to resolve this?
The schema is part of a standard, so I think there should be no error in the 
schema itself.
 
I appreciate if anyone can help me with this issue.

Thanks.