Entity parameter references that contain colons

[jt...@ebmail.gdeb.com]

I have found that if a DTD that I am using contains an entity parameter
reference that has been assigned a value that contains a colon  as in the
following declaration:

<!ENTITY % schema_instance "osb:uos">

and I use that entity parameter reference at a later point in my dtd as in:

<!ELEMENT express_data
 (data_section_header?, %schema_instance;)>
<!ATTLIST express_data
    id ID #REQUIRED
    representation_category NMTOKENS #REQUIRED
    name CDATA #IMPLIED>

<!ELEMENT osb:uos ANY>
<!ATTLIST osb:uos
     c    IDREFS         #REQUIRED
     unset     IDREF          #IMPLIED
     schema  NMTOKEN          #IMPLIED>


I will receive the following error during validation with Xalan (Java):

========= Parsing file:D:/xalan/samples/mjg/mjg.xml ==========
XSL Error: Could not parse file:D:/xalan/samples/mjg/mjg.xml document!
XSLT: String index out of range: 10
Xalan: was not successful.
XSLProcessor: done

This appears to happen for any entity parameter reference that contains a
colon.

If I remove the colon, or remove the various instances of the entity
parameter reference in the dtd then  the problem goes away.
Does anyone know why this is happening? As far as I can tell it is valid
xml.

Thanks,
Joe