Why do I get a checksum error when downloading updates via IGSS Update?
The checksum error is most likely caused by a running antivirus program. Disable the antivirus program entirely or disable checking of the [IGSS InstallPath]\gss\updates folder.
Some antivirus programs are known to prevent certain operations in IGSS. Refer to FAQ #43 – IGSS, Win XP SP2 and antivirus programs.