doesn't recognise ~ (PR#8096)

Full_Name: Leo van Romunde
Version: 2, 1, 0
OS: Win XP prof. sp1
Submission from: (NULL) (81.58.34.90)


When we type the following R gives an error:

a = c(1, 2)
b = c(1, 2)
boxplot (a ~ b)

Error in list(a, b) : invalid 'envir' argument

When we do exactly the same on another machine (Win2000) it works correctly.
Any suggestions?