[R] result of mean(v1, v2, v3) of three real number not the same as sum(v1, v2, v3)/3

[Sorkin, John]

I have a very strange problem. I am getting different results from 
mean(mlagFZ1,mlagFZ2,mlagFZ3)
vs. 
 sum(mlagFZ1,mlagFZ2,mlagFZ3)/3


> mean(mlagFZ1,mlagFZ2,mlagFZ3)
[1] -0.3326792

>  sum(mlagFZ1,mlagFZ2,mlagFZ3)/3
[1] -0.201942

R code:
print(mlagFZ1)
print(mlagFZ2)
print(mlagFZ3)
 sum(mlagFZ1,mlagFZ2,mlagFZ3)/3
mean(mlagFZ1,mlagFZ2,mlagFZ3)

output;
> print(mlagFZ1)
[1] -0.3326792
> print(mlagFZ2)
[1] -0.1890601
> print(mlagFZ3)
[1] -0.0840866
>  sum(mlagFZ1,mlagFZ2,mlagFZ3)/3
[1] -0.201942
> mean(mlagFZ1,mlagFZ2,mlagFZ3)
[1] -0.3326792

Can someone tell me what I did wrong?