your keyword "enable blending" reminded me!
i fixed,ex:
GlStateManager.enableBlend();
mc.getTextureManager().bindTexture(mapRaderBG);
drawTexturedModalRect(ModItemDurable.mapPosX, ModItemDurable.mapPosY, 0, 0, 256, 256);
GlStateManager.disableBlend();
in minecraft
Thank you very much.