[R] reading csv files - SYLK : file format not valid

[Bob Green]

I am wanting to read EXCEL files into R. In the past I have saved 
EXCEL files as csv files without difficulty. Recently, when I have 
saved the files in this format I am then unable to open them again in 
EXCEL or though windows (XP). I receive a message stating -  SYLK: 
file format not valid.

R will read the file, but I cannot open it in windows. Csv files 
created and saved in the past (on the same computer) can still be opened.

I am not saving as csv (Macintosh) and saving as a SYLK file results 
in the same error.

Any suggestions are appreciated,

Bob