Hi There is a bug in read.GenePix in marrayInput for Windows. The problem comes when I set path=NULL because I have the full path to my file in fnames. The offending line is: y <- readLines(file.path(path, fnames[1]), n=100) If path=NULL and fnames[1]="C:\\myfile.gpr", then file.path() returns something odd: > file.path(NULL,"C:\\myfile.gpr") [1] "/C:\\myfile.gpr" Clearly this is not a valid Windows resource lopcator! A quick fix, I guess, would be: if(is.null(path)) y <- readLines(file.path(fnames[1]), n=100) else y <- readLines(file.path(path, fnames[1]), n=100) Cheers Mick