This Joomla component is really great once you get it running! After a few minor difficulties, I have successfully installed MJ on a large site. Thanks to support from MJ!
Because of the specifics of mobile devices I have created a special menu for mobiles! Works well, even though some tweeks are still required.

Now in the "Advanced settings" of the component I have "Warnings" and about 100 lines like the ones below:

So what does this mean? What needs to be done about it?

Gratefull for any ideas, suggestions,...

It means that you have menu items with identical aliases. Joomla 1.6+ doesn't allow to create such items (because of it breaks router work), but Joomla 1.5 has no such a test of integrity. If you like to have special mobile menu, put ALIASES of "real" menu items here instead of new items with the same alias. Or use unique aliases.

The problem with such duplicates is that Joomla for path (e.g.) "/about-us" cannot choose correct Itemid if there are several items with "about-us" alias. In this case the choice is done randomly, and either you get mobile item on desktop template, or desktop item on mobile.