Mine did that also, you have either pushed the tools in too far, or you're not pushing them out enough. Try pushing them both towards the outside of the car more. If that doesn't work get the real tools. They usually work better, and they're $5 or so. You can find them at auto parts stores, or wal-mart.
Here is a
Mastersheet to help you.
Also, you do know that if you are replacing a factory CD player, you will need an amp bypass Crutchfield part number 12 70-5008.