I seem to have resolved this by changing search paths and hiding one file, but is still puzzling. I had changed the locations of two files, but not sure why that would cause this.
Also, I had been using a version of 'RegExpr.pas' that SynEdit may use. SynEdit compiled, but Lazarus may have found my copy and tried to recompile. Just a guess, I really have no idea.
BTW, I'm back at the current trunk.