GeneralBr3tt

I'm creating a temporary modpack but can't seem to get it to work. I keep receiving this error and I am desperately in need of finding out how to fix it. I have installed forge by the universal file. My modpack is being run on 1.7.2 [19:58:11] [main/ERROR]: The minecraft jar file:/C:/Users/Brett/AppData/Roaming/.technic/modpacks/reallife-172/bin/modpack.jar!/net/minecraft/client/ClientBrandRetriever.class appears to be corrupt! There has been CRITICAL TAMPERING WITH MINECRAFT, it is highly unlikely minecraft will work! STOP NOW, get a clean copy and try again! [19:58:11] [main/ERROR]: For your safety, FML will not launch minecraft. You will need to fetch a clean version of the minecraft jar file [19:58:11] [main/ERROR]: Technical information: The class net.minecraft.client.ClientBrandRetriever should have been associated with the minecraft jar file, and should have returned us a valid, intact minecraft jar location. This did not work. Either you have modified the minecraft jar file (if so run the forge installer again), or you are using a base editing jar that is changing this class (and likely others too). If you REALLY want to run minecraft in this configuration, add the flag -Dfml.ignoreInvalidMinecraftCertificates=true to the 'JVM settings' in your launcher profile.