Helium in the atmosphere. Evidence for or against a young earth?

Creationist websites such as Answers in Genesis are claiming that there is far too little helium in the atmosphere for the earth to be billions of years old. There argument is something like this:
Helium is produced by the decay of Uranium. It escapes from rocks fairly rapidly and enters the atmosphere. They agree that since helium is a very light gas, some Helium does escape into space, but there is still far more helium being added to the atmoshpere than escaping into space. Thus, because there is so little helium in the atmosphere, the earth cannot be very old.
(I am not very familiar with this subject, so can someone explain to me the flaws, if there are any, with this argument?However, I have seen evolutionists use a similar kind of argument against a young earth. The evolutionist argument is something like this: There is a lot more radioactive uranium in the world than radioactive potassium. I believe the ratio of radioactive potassium to radioactive uranium in the planet is something like 27/100 (?). Helium, as the creationists have admitted, diffuses from rocks much more rapidly than argon. Thus, if the earth is young, there should be much, much more helium in the atmosphere than argon because, as stated above, helium defuses faster than argon and much more helium gets produced than argon. Unfortunately for the creationists, there is about 2000 times more argon in the atmosphere than helium!!! How can this be if the earth is so young?[This message has been edited by EvO-DuDe, 07-27-2002]

The decay rate of Uranium is not much slower than radioactive potassium. The half life of U-235 is, in fact, considerably faster than the decay rate of K-40. The decay rate of U-238, however, is, as you said, a bit slower than the rate of decay for K-40. In the evolutionist model there has been enough time for most of the helium to escape into space. Thus, there is very little helium and lots and lots of argon. For the creationists, there should be lots and lots of helium (because there has not been enough time for large quantities of it to escape into space) and there should be very little argon (because argon diffuses slower than helium and there is more uranium than radioactive potassium)