Float exception in r.cover

[Milton ESALQ]

Dear grass guru's

I'm trying to compute the covariance matrix using
the r.cover program with this command:

        grass> r.cover -r tm1,tm2,tm3,tm4,tm5,tm7

        but the grass return the 'float exception'  message!

What are wrong?
What I do?

        Thanks in advance,

        Miltinho,
        Milton at nimbus.dpi.inpe.br