Nerves of steel achievement glitch

[thecrazyguy]

Ok, i was going for the nerves of steel achievement, and i did what the achievement guide said. I put the difficulty on 10, and got to 1,000,000 points without using a smart bomb, but the achievement didnt unlock! I tried it three times and no luck.

Has anyone else had these problems, or am i doing something wrong? Can anyone help me out with this?

Any help would me much appreciated