Custom CMSHtmlEditor and QuicklyInsertImage not working

Hi all,

I've made a custom web part that creates a page via some fields. One of those fields is a CMSHtmlEditor field.

<cms:CMSHtmlEditor ID="BodyEditor" runat="server" ToolbarSet="Noticeboard" IsLiveSite="true" />

BodyEditor.MediaDialogConfig.UseFullURL = true;
BodyEditor.LinkDialogConfig.UseFullURL = true;
BodyEditor.QuickInsertConfig.UseFullURL = true;

When I click the QuicklyInsertImage button and choose an image, the resulting image is not found. Chrome for example, reports the following:

Failed to load resource: the server responded with a status of 404 (Not Found)
http://intranet/getattachment/News-Events/Noticeboard/sample.png.aspx

This happens 90% of the time. The other 10% of the time, it works for no clear reason. Any ideas on how I need to identify the problem and fix it?