Ford Sued in Defective Door Latch Claim  DETROIT (Reuters) - A Canadian law firm on Tuesday said it  had filed a lawsuit against Ford Motor Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=F.N target=/stocks/quickinfo/fullquote"&gt;F.N&lt;/A&gt; over what it  claims are defective door latches on about 400,000 of the  automaker's popular pickup trucks and SUVs.