--- a/layout/generic/nsColumnSetFrame.cpp
+++ b/layout/generic/nsColumnSetFrame.cpp
@@ -1066,17 +1066,17 @@ nsColumnSetFrame::Reflow(nsPresContext* 
   
   CheckInvalidateSizeChange(aDesiredSize);
 
   FinishAndStoreOverflow(&aDesiredSize);
   aDesiredSize.mCarriedOutBottomMargin = carriedOutBottomMargin;
 
   NS_FRAME_SET_TRUNCATION(aStatus, aReflowState, aDesiredSize);
 
-  NS_ASSERTION(NS_FRAME_IS_COMPLETE(aStatus) ||
+  NS_ASSERTION(NS_FRAME_IS_FULLY_COMPLETE(aStatus) ||
                aReflowState.availableHeight != NS_UNCONSTRAINEDSIZE,
                "Column set should be complete if the available height is unconstrained");
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsColumnSetFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,

--- a/layout/generic/nsContainerFrame.cpp
+++ b/layout/generic/nsContainerFrame.cpp
@@ -894,24 +894,28 @@ nsContainerFrame::ReflowOverflowContaine
       }
     }
   }
 
   if (!overflowContainers)
     return NS_OK; // nothing to reflow
 
   nsOverflowContinuationTracker tracker(aPresContext, this, PR_FALSE, PR_FALSE);
+  PRBool shouldReflowAllKids = aReflowState.ShouldReflowAllKids();
+
   for (nsIFrame* frame = overflowContainers->FirstChild(); frame;
        frame = frame->GetNextSibling()) {
     if (frame->GetPrevInFlow()->GetParent() != GetPrevInFlow()) {
       // frame's prevInFlow has moved, skip reflowing this frame;
       // it will get reflowed once it's been placed
       continue;
     }
-    if (NS_SUBTREE_DIRTY(frame)) {
+    // If the available vertical height has changed, we need to reflow
+    // even if the frame isn't dirty.
+    if (shouldReflowAllKids || NS_SUBTREE_DIRTY(frame)) {
       // Get prev-in-flow
       nsIFrame* prevInFlow = frame->GetPrevInFlow();
       NS_ASSERTION(prevInFlow,
                    "overflow container frame must have a prev-in-flow");
       NS_ASSERTION(frame->GetStateBits() & NS_FRAME_IS_OVERFLOW_CONTAINER,
                    "overflow container frame must have overflow container bit set");
       nsRect prevRect = prevInFlow->GetRect();