Could you please turn this into a reprex? It's always helpful, but it's especially relevant w/ what you've got above as the quotation marks have been automatically turned into “ and ” (“” vs "").
I'm pretty sure this has nothing to do with Windows/Mac. I'm getting the error on Windows with R3.4.1. You could post which versions of R you are running. Somebody with more knowledge than me could state whether the behaviour of complete.cases changed between different versions of R.
I've got the same error with your code when run in macOS or Windows 10.
You have cleanly formatted code in your post which helps, but a reprex actually runs the code so we can see the errors you are seeing. Here is your code in the form of a reprex.
V3<-c(1,2,3,4,5,6,7,NA,19,NA,98,NA,NA)
V4<-c("A",NA,"B",NA,"C",NA,"D",NA,"E","F","G",NA)
E<- complete.cases(V3,V4)
#> Error in complete.cases(V3, V4): not all arguments have the same length
E
#> Error in eval(expr, envir, enclos): object 'E' not found
V3[E]
#> Error in eval(expr, envir, enclos): object 'E' not found
V4[E]
#> Error in eval(expr, envir, enclos): object 'E' not found