"If you REALLY want to run minecraft in this configuration, add the flag -Dfml.ignoreInvalidMinecraftCertificates=true to the 'JVM settings' in your launcher profile."
Reading the logs...
Sometimes windows does not find the starting class. So does mine.
You can start the installer for build 845 with this command:
java -cp minecraftforge-installer-1.6.2-9.10.0.845.jar cpw.mods.fml.installer.SimpleInstaller
The starting class "cpw.mods.fml.installer.SimpleInstaller" can be found in the META-INF folder in MANIFEST.MF.
Eclipse shows row 239 as a problem and won't compile.
IOUtils.closeQuietly(zf);
zf is from wrong type. Should be "Reader" instead of ZipFile.
However, you can replace it with
zf.close();