[BioC] LIMMA- Warning message after eBayes function

[Ankit Pal]

Dear all,
On running the eBayes function in LIMMA, I got the
following
error.

> fit_NODS7 <- eBayes(fit_NODS7)

Warning message: 
Estimation of var.prior failed - set to default value
in: ebayes(fit = fit, proportion = proportion,
stdev.coef.lim = stdev.coef.lim)

What does it mean?
I know that the data is passed from the lmFit() step
to the eBayes() step without intervention from the
user. It worked for a couple of experiments and for
the third set,  gave the above error.
Thank you,
-Ankit