I have updated the Stock Quotes web part to fix the overflow error when certain stocks would have very high volumes:
System.OverflowException: Value was either too large or too small for an Int32. at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) at StockQuotes.StockQuotes.RenderStockQuotes()
I have changed the parse object to be an uInt64, so it should be a while before we see enough volume to experience this problem again.
You can download the updated version from the link in the main Stock Quotes post.