I may have the answer for you.
Here is what I did.
1. Uninstall totally this plugin. Verify everywhere it is gone. Site will likely still be a mess.
b. Delete all site cookies, clear cache, purge expired, etc.
2. Check /administrator/language/ (your language) to make sure it is still there. Mine got deleted totally.
If deleted, you have to find the installs for all your plugins and see if there is any language files they load into that folder. Use your install version of Joomla to find that folder and upload it to the same folder with the same structure.
3. Install Mobile Joomla again. Do not adjust anything yet. Watch for errors of SQL.. If this happens, I can give you an SQL file to inject manually.
4. Now the odd part.... go to administration area -> Extensions Menu -> Template manager
a. Look at the template list, and you will see 4 with check marks. Go in to each and assign to a separate menu range...
a1.To do that you have to create a separate menu for each first. (Use menu Manager using the main menu of your site, copy, and customize from there for each device. Make 4. Name as mainwap, mainiphone, mainimode, mainpda works... , this makes it easy to keep it straight what they are. But... make sure you rename each alias ie. home to home-iphone. Forgot that on some menu items, and it really made a mess, as then it would give that "illegal use..." message again, and I would have to track down each wrong menu link alias.
The make sure link them up in the correct main modules for each of the types of mobiles (imode, iphone, wap, pda)
Any errors now generated is likely a menu link alias issue. or some menu being assigned to the main menu, when it can only be assigned to the respective mobile mode.
NOTE: You can test that the PC can view first by just assigning each to only one DIFFERENT menu item.
I opened the template, clicked on one menu item, then clicked save. Have read that some people have had problems with save in these files. When done, you should see 4 checkmarks in the template manager window. If it is less, I think it means some are assigned to the same menus. A small attempt at avoiding this issue.
Hope that works.... If it does, you owe me a Limoncello next time I am in Italy
Sincerely,
Kirk B