Early in my R life I discovered the pain of R and windows being on different pages when it came to the separator between directories and subdirectories. Eventhough I know about
You could create a wrapper function around all path names:
> replace.slash <- function(path.name) gsub("\\\\","/",path.name)
> path.name <- "c:\\tmp\\"
> replace.slash(path.name)
[1] "c:/tmp/"
[Edit]: Thanks Hadley. I corrected the error there.
Incidentally, I found this very useful discussion on this subject.