[R] Error message - what does it mean???

[Monica Palaseanu-Lovejoy]

Hi,

I am trying to calculate mahalanobis distances for a matrix x with 
n*p variables. I am getting the following error:

md2 <- mahalanobis(x, center, cov)
Error in solve.default(cov, tol = tol.inv) : 
        system is computationally singular: reciprocal condition 
number = 2.11165e-009

What does it means?

Thank you so much for any help,

Monica