I need to create a simple list with an AD user column but when I try to add a new item I get an 'Unexpected error' if the username has been checked, if the username has not been checked and corresponds to a user in the AD I can proceed and it saves correctly.

The unexpected error message is:

System.InvalidOperationException: Namespace prefix 'xsd' is not defined. at System.Xml.Serialization.XmlSerializationReader.ToXmlQualifiedName(String value, Boolean decodeName) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderDictionaryEntryArray.Read1_Object(Boolean isNullable, Boolean checkType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderDictionaryEntryArray.Read2_DictionaryEntry(Boolean checkType) at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderDictionaryEntryArray.Read3_ArrayOfDictionaryEntry()

Which doesn't help me much..


2 Answers 2



I had the same problem and for a long time there were no answers out there for anybody. Then I saw the question hotfix for problem with SharePoint PeopleEditor in IE-9 and a person there had posted an answer that led me in the right direction. You could try his solution or mine, which I also posted as an answer to that question.



  • You deserve more likes for spreading this article.
    – Alex
    Oct 8, 2013 at 19:29

I've run into the same issue. Your pages probably tell IE to use IE9 standards, i.e. you have a

<meta http-equiv="X-UA-Compatible" content="IE=9"/>

tag in your master page.

The problem is, this doesn't work with people picker. Please see this discussion: http://social.msdn.microsoft.com/Forums/en/sharepoint2010general/thread/90b3835c-6754-4bb6-9fd4-b74f16f236ff.

I haven't found a fix yet, just saw the workaround mentioned in the discussion -- i.e. you have to go back to using IE8 standards. That's not a good option for us, because we'd like to use CSS3.

  • jaleikas, please follow the link in my answer, there is a solution there.
    – Matt
    Apr 24, 2012 at 14:06

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