Access Denied in IE6

First of all - great module, it really makes things a lot easier when it comes to publishing content. However, we are having trouble with IE 6.

We have a site which has 2 themes, one for public consumption, and one for members only. When a registered member signs in, they have the ability to add content, however when using IMCE, it seems that IMCE forgets about the user's session info, and throws an 'Access Denied' error back at the user when they click the Browse button.

I can tell that the session information gets neglected, as the site changes back to the 'public' theme just before the error is displayed.

This error does not occur in Firefox, only in IE.

Does anyone have any ideas?