Problem with gam() after R update

Dear group,
I experience s?ome problems with gam() function after R update to version 2.13.1
The function in both gam and mgcv packages stopped to work. Before, with the same code I used, everything was fine.
The function from gam package yields following warning:

 Residual degrees of freedom are negative or zero.  This occurs when the sum of the parametric and nonparametric degrees of freedom exceeds the number of observations.  The model is probably too complex for the amount of data available

while gam() from mgcv crashes R.

Did I miss something?

Thank you in advance.

PJ