I had the exact same problem this week. Does it say Systemmenu v0? What version of IOS does it say above that?
I had to get the homebrew channel dol, install the file and then get preloader to autoboot to file (do that in settings) as it wont run it straight from Load File in preloader. Then once it booted into the homebrew channel after a reboot (which many involve pulling the plug out to do so) i ran wad manager and installed the system menu from a wad file (find it on the net) v289 for NTSC and v290 for PAL. I got the update from a rescue disc found on rapidshare and then extracted the update using wii scrubber.
You may need to install an IOS first before the system menu but not sure on that one.
Once I did that i went through the entire softmod process again to get it back up and running but made sure that i ran hack remover before i reinstalled preloader.
This is the only way to fix it if you dont have a network connection as all the software installers connect to nintendo's servers - at least that's what i found anyway, especially after trying to run all sorts of boot.dols and getting code dumps.
Hope you fix it pal.