Frozen script editor window while R console is computing

R for MAC experts:

When using the current version of R for MAC, I notice a troublesome  
behavior.  Sometimes I need to build complex regression models  
(usually using lmer) or simulations that take 10 minutes or more for  
the computer to compute.  While this computing is going on, I would  
like to be able to take advantage of this "free time" to write more  
code.  But I can't! In my current setup of R for MACs the script  
editor is frozen while the console is computing. That means that my  
only recourse is to go for a 10 minute coffee or to the toilet.  I  
don't believe that my windows version of R has this same problem.

My question:  Is there a way to set R for MAC up so that the script  
editor window is functional while the console window in chomping away  
at some calculations?

Brant Inman
Duke University