This should be an FAQ or something...
It's a Yahoo problem, they stopped sending 52-week data in their CSV data downloads for many tickers. When I asked them about it, their response was
"The 52-Week range data that you may have received previously is no
longer included in the CSV downloads that come from Yahoo! Finance."
So it doesn't look like they are going to fix it. Feel free to complain to Yahoo, maybe if enough people do it, they will fix it.