diff -Naur flock/defaults/pref/flock.js flock.src/defaults/pref/flock.js
--- flock/defaults/pref/flock.js	2009-08-07 19:41:52.000000000 +0200
+++ flock.src/defaults/pref/flock.js	2009-09-30 08:01:35.000000000 +0200
@@ -404,6 +404,7 @@
 pref("browser.xul.error_pages.expert_bad_cert", false);
 
 // We want to make sure mail URLs are handled externally...
+pref("network.protocol-handler.app.mailto", "/usr/bin/thunderbird");
 pref("network.protocol-handler.external.mailto", true); // for mail
 pref("network.protocol-handler.external.news", true);   // for news
 pref("network.protocol-handler.external.snews", true);  // for secure news
diff -Naur flock/flock-browser flock.src/flock-browser
--- flock/flock-browser	2009-08-07 19:41:51.000000000 +0200
+++ flock.src/flock-browser	2009-09-30 08:02:43.000000000 +0200
@@ -52,7 +52,15 @@
 #uncomment for debugging
 #set -x
 
-moz_libdir=/usr/local/lib/flock-2.5.2
+moz_libdir=/usr/local/flock-2.5.2
+
+# Include /usr/lib/mozilla/plugins in the plugin path:
+if [ "$MOZ_PLUGIN_PATH" ] ; then
+  MOZ_PLUGIN_PATH=$MOZ_PLUGIN_PATH:${moz_libdir}/plugins:/usr/lib/mozilla/plugins
+else
+  MOZ_PLUGIN_PATH=${moz_libdir}/plugins:/usr/lib/mozilla/plugins
+fi
+export MOZ_PLUGIN_PATH
 
 # Use run-mozilla.sh in the current dir if it exists
 # If not, then start resolving symlinks until we find run-mozilla.sh