Hi Spyder, I don't actually have a blade SRX 200 but it is common to most helicopter when something is not right.
1. Is the tail rotor on the right way around, normally aerofoil section facing away from the boom.
2. Is the gyro working correctly, with the helicopter powered up hold it (very tightly) away from you, move the tail left or right, the tail motor should start on try to pull the tail in the opposite direction.
3. Is the tail motor in good condition, maybe it is not producing the power it used too.