The documentation for MetaData indicates that when the attribute list is empty, it should be scala.xml.Null (not null). Block quotes and footnotes return an element with a null attribute list:

(TextileParser.toHtml("bq. Block quote") \ "p").map(_.attributes).first

Here's a short patch:

--- lift-textile/src/main/scala/net/liftweb/textile/TextileParser.scala Fri Oct  9 23:22:53 2009
+++ lift-textile_patch/src/main/scala/net/liftweb/textile/TextileParser.scala   Fri Oct  9 23:22:37 2009
@@ -995,7 +995,7 @@

   case class BlockQuote(elems : List[Textile], attrs : List[Attribute]) extends ATextile(elems, attrs) {
     override def toHtml : NodeSeq = {
-      val par : NodeSeq = XmlElem(null, "p", null, TopScope, flattenAndDropLastEOL(elems) : _*) ++ Text("\n")
+      val par : NodeSeq = XmlElem(null, "p", Null, TopScope, flattenAndDropLastEOL(elems) : _*) ++ Text("\n")
       XmlElem(null, "blockquote", fromStyle(attrs), TopScope, par : _*)  ++ Text("\n")
     }
   }
@@ -1023,7 +1023,7 @@
   case class Footnote(elems : List[Textile], attrs : List[Attribute], num : String) extends ATextile(elems, attrs) {
     override def toHtml : NodeSeq = {
       XmlElem(null, "p", fromStyle(AnyAttribute("id", "fn"+num) :: attrs), TopScope,
-              (XmlElem(null, "sup", null, TopScope, Text(num) : _*) :: flattenAndDropLastEOL(elems)) : _*) ++ Text("\n")
+              (XmlElem(null, "sup", Null, TopScope, Text(num) : _*) :: flattenAndDropLastEOL(elems)) : _*) ++ Text("\n")
     }
   }