Hi,
Joomla modules are displayed on pages by looking at "itemId" of that pages.
When you create a Joomla menu item, that item gets an item-id.
If you set your Virtuemart Frontage as your Joomla homage, it will get a specific itemID, but the thing is; all the other virtuemart pages (that doesn't associated with any menu-item) will have the same itemId as your homepage menu-item. Therefore, the module you try to publish on homepage will be visible on some other pages as well, because of the similar itemid.
For better understanding, disable the SEF URL, and check the URL of the pages (pay attention to itemId parameter)
This is how Joomla works. (not Virtuemar's fault, not Sportmart's fault)
Try this extension:
extensions.joomla.org/extensions/style-a-design/modules-management/3391
This extension will let you publish module on specific pages (not on specific itemId). So, even though some pages sharethe same itemID, modules will be displayed only on the pages you want.
Regards.
Support