R – Incomplete final line when trying to read csv in R

I've got R v.2.15.1 running on Mac OS 10.8.2 . Earlier today, R started throwing errors at me every time I try to import ANY recently created (today) csv files. Older (before today) csv files work fine, but anything I create that's new will not read in without a warning.

I'm creating the csv's the same way — saving the spreadsheet as .csv in MS Excel (Office for Mac 2011).

Even with a dummy file ('test.csv'), I get this:
"Warning message:
In read.table(file = file, header = header, sep = sep, quote = quote, :
incomplete final line found by readTableHeader on 'test.csv'"

in TextEdit, test.csv is:

cat,stuff
1,1
2,2

I have tried hitting enter at the end of every line (as suggested here: 'Incomplete final line' warning when trying to read a .csv file into R ) , but this doesn't work.

I've re-installed R and Microsoft Excel. Weirdly, I was able to read in the csv file without a warning on a Windows machine with R. On another Mac with R and also with RStudio, I get the same warning…

I know this is "just" a warning, but it makes me a bit nervous and seems to have the potential to cause problems in the future.