More creationist misrepresentation.
The first example was the application of potassium-argon dating to very young rocks, which is entirely inappropriate. This is specifically covered in the article I gave you before:
Radiometric Dating
It also tells you how we know that these methods work and how they are checked. Why not read it, if you're not afraid of the truth? It's even written by a Christian.
Radiometric dating--the process of determining the age of rocks from the decay of their radioactive elements--has been in widespread use for over half a century. There are over forty such techniques, each using a different radioactive element or a different way of measuring them. It has become increasingly clear that these radiometric dating techniques agree with each other and as a whole, present a coherent picture in which the Earth was created a very long time ago. Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers. Many Christians have been led to distrust radiometric dating and are completely unaware of the great number of laboratory measurements that have shown these methods to be consistent. Many are also unaware that Bible-believing Christians are among those actively involved in radiometric dating.
On the specific point:
Some young-Earth proponents recently reported that rocks were dated by the potassium-argon method to be a several million years old when they are really only a few years old. But the potassium-argon method, with its long half-life, was never intended to date rocks only 25 years old. These people have only succeeded in correctly showing that one can fool a single radiometric dating method when one uses it improperly. The false radiometric ages of several million years are due to parentless argon, as described here, and first reported in the literature some fifty years ago. Note that it would be extremely unlikely for another dating method to agree on these bogus ages. Getting agreement between more than one dating method is a recommended practice.