PS graphs in R 2.6.0

Dear R-users:

I have been working in R for few years and never I'd been the problems like this. I'm running the last R version and when I try to save a graph in PS format I have the next error

Error: Invalid font type
In addition: Warning messages:
1: font family not found in PostScript font database 
2: font family not found in PostScript font database 

I thinks it's curious because using R 2.5.1 I didn't have this result. Could somebody please explain me what happen? 


Thanks in advance,

Jorge Ivan Velez
Industrial Engineer
Master in Sciences (Candidate)
Faculty of Sciences
School of Statistics
National University of Colombia at Medellin
Medellin, Antioquia, Colombia 
e-mail: jivelez at unal.edu.co