Hi,
I have noticed that the Product Detail URL uses the parameter "ctl" and as far as I know if DotNetNuke sees the parameter "ctl" in the URL, it will load only the module that has it's module ID in the URL, and assign the Admin Skin set in Site Settings under the Appearance section.
This has stopped us from adding other modules to the page, and we desperately need this feature to be able to place other up-sale content. This also causes confusion as we do need a different skin for the module which differs from the Admin Skin.
Here is an article which explains the correct way of implementing the module when there are multiple interfaces:
http://www.apptheory.com/dotnetnuke/articletype/articleview/articleid/141/avoiding-the-dotnetnuke-admin-skin.aspx
Hope this will be fixed in the up-coming releases.
Cheers,
Cassie