hi Ivo! 

First of all thanks for replying me... 

> hi, emeric! 
> 
> [...] 
> 
>> Does anyone know the source of the problem ?
> 
> well... first of all: which platform are you working on?! 
> 
> maybe it's a platform-side problem and doesn't occur on all machines... 
> 
> ivo 
> 
> 

I am working under linux and I still have the same problem. I saw somewhere 
in the swiki that it (NaN error) was a platform specific problem but I found 
no answer to my questions...