Mind you that I am using the DSx - but the Arm7 fix has worked for me in getting Zelda PH (J), SimCity (U), all the Megaman Starforce games (U), DK Swing whatever it's called(j) and Drawn to Life (U) to work.
After you've downloaded the Arm7 zip file you'll notice that there is a DONOR and a PATIENT folder. Get the SimCity JAPANESE rom and place that in the DONOR folder. Essentially, the Arm 7 fix removes a file (I think that it's associated with the save type) from the SimCity J rom and modifies your problem rom (Megaman Starforce, for example) by placing that file in the rom.
So with the SimCity J rom in the DONOR folder, place your problematic rom in the PATIENT folder. After that just click the Fix.bat file, type Y, hit enter and watch it do it's stuff. When you're done you'll find a new rom in the Arm7 fix folder - rename it to whatever the rom was that you placed in the PATIENT folder and you should be all set with a working rom.