I had that problem with the publisher module. It happens that I was using global $adminmenu.

My solution was not to use the global $adminmenu but create my own global $publisher_adminmenu. Then in admin/menu.php, just after defining my menu, I used $publisher_adminmenu = $adminmenu (which contain my menu).

What happens is that core 'module' class uses include_once to include your menu. So if you are using a global variable and she gets overwrited by other modules you will not be able to use the class method to include your file again and overwrite that global with the correct value.

The correct solution is to fix this in module has I did, but you can also hack OXIGEN. Just edit system/guy/oxigen/oxigen.php

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if (is_object($xoopsModule) || !empty($_GET['xoopsorgnews'])) {
return;
}


And add an extra line like this:

if (is_object($xoopsModule) || !empty($_GET['xoopsorgnews'])) {
@include XOOPS_ROOT_PATH.'/modules/'.$xoopsModule->getVar('dirname').'/'.$xoopsModule->getInfo('adminmenu');
return;
}


This will force the menu to be included again and populate the global with the correct values.

Sorry if I cannot explain me better.