Some player report the error about the Compatibility for other mod(e.g. Ars Magica 2).I found the same problem as belaow:

According to error log,the problem function in other mod is:

public void func_150895_a(Item p_150895_1_, CreativeTabs p_150895_2_, List p_150895_3_) {
this.field_150939_a.func_149666_a(p_150895_1_, p_150895_2_, p_150895_3_);
}

then in this mod is:

public void getSubItems(Item p_150895_1_, CreativeTabs p_150895_2_, List p_150895_3_)
{
    p_150895_3_.add(new ItemStack(p_150895_1_, 1, 0));
}

and throw java.lang.NullPointerException: Initializing game .

Use the Large Sign1.1, and Forge1232, this problem has been settled.