Download for model i9020T, i9023 and build GRI40 and baseband KB1

(http://android.clients.google.com/packages/ota/google_crespo/a14a2dd09749.signed-soju-GRJ22-from-GRI40.a14a2dd0.zip)

Download for model i9023 and build GRI54

(http://v7.nonxt6.c.android.clients.google.com/packages/data/ota/google_crespo/486786a7fd97.signed-soju-GRJ22-from-GRI54.486786a7.zip)

To update manually follow the instructions at http://nolovelust.com/post/Nexus-S-receives-second-OTA-update-353e267378cdsigned-soju-GRH78C-from-GRH78353e2673zip.aspx

Changes on this update are as follows:

New: Video chat in Google Talk

Bug fix: Phone shuts down or reboots

Bug fix: Wi-fi & 3G icons both indicate active

Bug fix: Battery life

Bug fix: GPS location/navigation

Via http://www.google.com/support/forum/p/Google+Mobile/thread?tid=3812c1acf93b482f&hl=en

Update 26/02/2011 : You should download latest android 2.3.3 instead of below

Android 2.3.2 update for Nexus S is only 600kb, it fixes SMS bug where messages gets sent to different numbers also addressing Nexus S random reboot issue.

Download it from here

Installation instructions taken from http://www.redmondpie.com/download-and-install-android-2.3.2-on-nexus-s-how-to-guide/ 

Copy this file to the root of your SD card

Now power off your phone, hold down the “Volume Up” button, followed by the “Power” button to turn it back on.

Now use the volume rocker buttons to navigate to “Recovery” option and then select it using “Power” button.

Now when you see an exclamation mark –like image on the screen, hold down the “Power” button followed by “Volume Up” button.

At this stage you should be presented with Android’s Recovery menu. Now select the option to apply the update from SD card, followed by selecting the actual update “.zip” file using the “Power” button.

That’s it. Wait for the phone to complete the update process. Once its done, select “reboot system now” option to reboot your phone into Android 2.3.2 Gingerbread.

Can't download Ms Security Essentials latest virus definition updates? Here are the fixes

Use http://go.microsoft.com/fwlink/?LinkID=87342 to download and install them manually

OR

You can also try below commands from command line

on XP: proxycfg -u

on Windows Vista/Windows7: netsh winhttp import proxy ie