Dyfrig,
Apologies for the delay. I just returned from holiday yesterday and have been working on getting some of these tickets cleaned up. I was unable to replicate your issue, but based on the call stack you sent over, I updated a few items that should hopefully resolve that issue. If you go to your downloads area of your account, you should be able to download the latest version 4.0.4 to see if that fixed the issue. If not, then you may need to throw it up on a dev site so I can take a deeper look.
Adam