Getting Quotes from Yahoo

The following R code was working for me:

     library(quantmod)
     start <- as.Date("2000-01-01")
     end <- as.Date("2018-04-05")
     getSymbols("^GSPC", src = "yahoo", from = start, to = end)

However, when I run it, I now get the error message:
     Error in curl::curl_download(cu, tmp, handle = h) :
     Failed to open file 
C:\Users\rsher\AppData\Local\Temp\RtmpeC1j1m\file28e81b02c31.

The machine has disk space. What am I doing wrong?

Bob Sherry