Sorry if I was unclear. The XML data is not corrupt. It appears that LibXML cannot load an 80MB XML without corrupting its own data. When I search within the XML, I do not find the offending parser error on line 85, or anywhere in the file.

So, I believe it to be a size limitation that causes internal memory management issues. Why 85th line? Maybe a pointer wrapped and happened to clobber the 85th line. Who knows. :/