Constant error messages with new R version

Hi I would be grateful if anyone could shed any light...
I usually import files into R with the read.csv command. This worked fine 
until I downloaded the latest version of R. Now, presumably it wont recognise 
the file as a data frame since I always get the error message:- 
"The following object(s) are masked from package:base :"
Any suggestions much appreciated,
Simon.




Simon Pickett
Centre for Ecology and Conservation Biology
University of Exeter in Cornwall
Tremough Campus
Penryn 
Cornwall
TR10 9EZ UK
Tel: 01326371852