Docs on http://www.stylecop.com/docs/SA1502.html say 'ElementMustNotBeOnASingleLine' ('A' between On and Single). It should be 'ElementMustNotBeOnSingleLine'.
This should be fixed in the header as well as in the How to Suppress Violations section.

See http://stylecop.codeplex.com/workitem/6770 as this issue was caused by this wrong documentation.