There are two possible reasons for this:
1: The Nostromo N50 software can cause a re-occuring looping patch. To get the patch to work please right-click the N in the system tray and shut it down. This should allow the patch to successfully go through.
2: Having a virus resident on your PC has also been known to cause the patcher to loop. Please be sure to run the latest anti-virus software to scan for any resident viruses that may reside on your system. You may visit http://housecall.trendmicro.com to use a free online scanner.