I have tried to get historical mtgox closing prices from both

http://bitcoincharts.com/t/trades.csv

You need to specify the symbol you want (e.g. mtgoxUSD in your case):

http://bitcoincharts.com/t/trades.csv?symbol=mtgoxUSD

Also, if you want the complete history you need to set a start timestamp:
http://bitcoincharts.com/t/trades.csv?symbol=mtgoxUSD&start=0

Can you explain to me how I can get them with timestamps? My browser just shows me the the content of a .csv file and I cant really use it.