[ESS] hitting return won't move the cursor down

[Tiago R Magalhaes]

Hi

I have upgraded to the ESS-5.2.6 and now when I hit return at the end 
of the line, the cursor won't go down - although a new line is 
created and I get the following message

"Symbol's value as variable is void: enable-multibyte-characters"

I didn't change any setting - at least voluntarily - and I was 
wondering if there's any way to get back to the previous behaviour: 
hiting return "creates" another line AND moves the cursor to it.

I am using a mac powerbook G4, OSX 10.3.8

Thanks for any help