CS4 Media Encoder waits 20 min before starting

Question

When I export media (flv-video or mp3-audio) after I hit the 'Start Queue' button the Media Encoder just waits(?) for 20 minutes before it actually starts encoding. During that 20 min elapsed time remains at 0:00:00, PProHeadless.exe uses CPU at 45% and nothing else. After 20min 'elapsed queue time' jumps straight to 00:20:xx and starts counting, CPU crunches at 100% etc. as if nothing is wrong.
Annoying especially when exporting short mp3-files... Any ideas, anyone?

Answer 1

Everyone may have already got what they wanted from the answers given in the post but I thought I'd add my PAL experience of this.
I tried to media export a timeline to one large mixdown file. (blackmagic mjpeg) the timeline had simple premiere titles fading up and down to black before each video module.  The media encoder worked fine but none of the dissolves from timeline to title worked - they translated as cuts in the mixdown.  In the end I dropped premiere generated black video over the titles and used variable opacity to bring them in and out.  This worked fine and proves that you can export with black at the front.
What it proves however is that CS4 really is working differently to CS3 in lots of ways.
As far as media encoder is concered, I'm sure this is a grandmother sucking eggs business but it's critical for performance that the USE PREVIEW FILES option in the settings box is selected.  Otherwise CS4 starts to re-render everything and seems to be much slower at doing it than a basic timeline render. Including metadata files doesn't seem to offend too much but I only evr include this when I'm exporting final versions anyway.