Index: /trunk/src/VBox/Additions/linux/installer/vboxadd.sh
===================================================================
--- /trunk/src/VBox/Additions/linux/installer/vboxadd.sh	(revision 74890)
+++ /trunk/src/VBox/Additions/linux/installer/vboxadd.sh	(revision 74891)
@@ -224,5 +224,5 @@
     begin "Starting."
     # If we got this far assume that the slow set-up has been done.
-    QUICKSETUP=yes
+    QUICKSETUP=start
     if test -z "${INSTALL_NO_MODULE_BUILDS}"; then
         uname -r | grep -q -E '^2\.6|^3|^4' 2>/dev/null &&
@@ -380,4 +380,14 @@
     info "Building the VirtualBox Guest Additions kernel modules.  This may take a while."
 
+    # If the kernel headers are not there, wait at bit in case they get
+    # installed.  Package managers have been known to trigger module rebuilds
+    # before actually installing the headers.
+    for count in 1 2 3 4 5; do
+        test "x${QUICKSETUP}" = xyes || break
+        test -d "/lib/modules/${KERN_VER}/build" && break
+        printf "Kernel modules not yet installed, waiting five minutes (%s of 5)" "${count}"
+        sleep 300
+    done
+
     log "Building the main Guest Additions module."
     if ! myerr=`$BUILDINTMP \
@@ -464,6 +474,7 @@
     cat << EOF > /etc/kernel/postinst.d/vboxadd
 #!/bin/sh
-test -d "/lib/modules/\${1}/build" || exit 0
-KERN_VER="\${1}" /sbin/rcvboxadd quicksetup
+# Run in the background so that we can wait in case the package installer has
+# not yet installed the kernel headers we need.
+KERN_VER="\${1}" /sbin/rcvboxadd quicksetup &
 exit 0
 EOF