--- a/mail/components/im/themes/chat.css
+++ b/mail/components/im/themes/chat.css
@@ -111,23 +111,18 @@ imgroup {
 .conv-top-info {
   margin: 0 0;
   padding: 0 0;
   border-style: none;
   -moz-appearance: none;
 %ifdef XP_MACOSX
   /* Copy of .main-header-area from pinstripe/mail/messageHeader.css */
   color: #2E3436; /* Aluminium 6 */
-  background: -moz-linear-gradient(top, #909090, #FFFFFF 5px);
-  border-bottom:1px solid #BFBFBF;
+  border-bottom:1px solid #BFBFBF !important;
   padding: 0.6ex;
-}
-
-.conv-top-info:-moz-window-inactive {
-  background: -moz-linear-gradient(top, #CDCDCD, #FFFFFF 5px);
 %else
   background-color: -moz-Dialog;
 %ifdef XP_WIN
   background-image: -moz-linear-gradient(rgba(255,255,255,.5), rgba(255,255,255,0));
 %else
   background-image: -moz-linear-gradient(rgba(255,255,255,.3), rgba(255,255,255,0));
 %endif
 %ifndef XP_WIN

--- a/mail/themes/pinstripe/mail/chat.css
+++ b/mail/themes/pinstripe/mail/chat.css
@@ -32,16 +32,21 @@
 }
 
 #listPaneBox > * {
   background: transparent !important;
   -moz-appearance: none !important;
   border: none;
 }
 
+/* Set a background color to avoid lightweight theme backgrounds */
+#contextPane {
+  background-color: #FFFFFF;
+}
+
 /* Adaptation of #searchInput from pinstripe/mail/searchBox.css */
 /* it looks like appearance: searchfield gets us our search icon... */
 #IMSearchInput {
   margin: 3px 4px 4px !important;
   -moz-appearance: searchfield;
   font: icon;
   height: 22px !important;
 }