The following in lyxmacros.inc is interferring with the address def in amsdefs.inc.
Style Address Margin Static LatexType Command LatexName lyxaddress ParSkip 0.4 BottomSep 1.5 ParSep 1.5 Align Left AlignPossible Block, Left, Right, Center LabelType No_Label # define the macro \lyxaddress Preamble \newcommand{\lyxaddress}[1]{ \par {\raggedright #1 \vspace{1.4em} \noindent\par} } EndPreamble End For the moment I've moved lyxmacros.inc above amsdefs.inc in amsart.layout. This is not very clean though. Best, Ed.