BlackBerry,
You can download the patch here instead of using Windows Update:
But first try to stop the restarting process:
Boot to Safe Mode.
First open task manager, find and end the process 'msblast.exe' If it is there.
Second, delete the registry key:
HKLM\Software\Microsoft\Windows\CurrentVersion\Run
Find the value windows auto update
if its value in the right panel is C:\windows\system32\msblast.exe delete the key.
Finally, delete the file c:\windows\system32\msblast.exe
reboot.
Logon as Administrator.
Don't try the Internet yet. Enable the Windows native Firewall.
Start, Run, services.msc
See if the Remote Procedure Call service is started. If not try to start it.
If it is running, go to the Internet and get the patch.
Even if msblast.exe is not there, by enabling the native firewall you should have enough breathing room to download and apply the patch.