The serial number "LU" means your wii is of the USA region. Even wiidrives.com has this to say about LU528: "The console has model number RVL-001(USA), produced for Mexico/Canada/USA."
From the HBC, run syscheck and copy and paste the results for us to see.
You're not supposed to have the option to install bootmii from the HBC. Download the hackmii installer and save the boot.elf to SD:\apps\hackmii\boot.elf, then run it from the HBC. When it loads, install bootmii (@ boot2 if possible), then run bootmii (by pressing home in the HBC and selecting bootmii) and make a nand backup.
Instead of whatever I started writing above, lets do this the easy way shall we?
Download ModMii from my signature, run the ModMii Wizard, when asked if your Wii is a virgin, say yes even though it isn't, when asked what your current firmware is, tell it that it is "4.2", tell it that the region is "U", and tell it that your desired firmware is "4.1". Answer the remaining questions however you like. Then let it download and build you a guide. Follow the guide exactly except instead of using Bannerbomb v2 to launch the hackmii installer, just load it from the HBC like you would anything else.
Following the above instructions, you'll install\update bootmii and the HBC, make a nand backup (very important for brick protection), install the 4.1U system menu and system menu IOS (which is what should fix your problem), and reinstall priiloader (as it woulda been uninstalled when you installed the 4.1U system menu). On top of that, it will also update your cIOSs and active IOSs, and if u selected them it will also install a custom theme and extra brick protection.
Good luck!