To disable the tab from displaying for people that don't have the XBox Live service, you just need to change some of the plugin code.
For the simple fix, change the first line of your plugin
Xbox Live Info Tab (it's at the
member_build_blocks_start hook) code to:
Code:
if ( $vbulletin->options['xblinfo_enable_product'] AND $userinfo[ $vbulletin->options['xblinfo_fieldid'] ] )
{
Altered code is in red. It's not the most efficient code, but it should work fine.