RMA problem in affy package

Question

[Nitin]

Hello,

I wrote following R code to analyze affymeterix microarray data

library(BiocGenerics)
library(methods)
library(Biobase)
library(affy)
library(limma)
library(statmod)
library(AnnotationDbi)
library(DBI)

targets <- readTargets ("affy_targets.txt")
data <- ReadAffy(filenames=targets$FileName)
eset <- rma(data)
pData(eset)

But at this step while executing showed following error

Error in function (classes, fdef, mtable) : 
  Unable to find an inherited method for function 'rma' for signature '"AffyBatch"'`

I am using this code from past 1 year with R 2.15.2 (now also I have used same version) which worked perfectly all the time. But today it ran into error..

Just not able to resolve this :(

Can anybody please help

Thanks,
Nitin