http://www.dpreview.com/news/0201/02012101canonnewfirmware.asp
http://www.canon.co.jp/Imaging/PSG1/PSG1_Firmware-e.html
G2:
http://www.canon.co.jp/Imaging/PSG2/PSG2_Firmware-e.html
Pro90IS:
http://www.canon.co.jp/Imaging/PSPRO90IS/PSPro90IS_Firmware-e.html
G1:Canon has today released new firmware for the G1, G2 and Pro90IS. For the G2 it is labelled version 1.0.1.0 and for the G1 / Pro90IS it is labeled version 1.0.0.3. These firmware updates both address the same issue: "With Firmware Version nnn, BP-511 or BP-512 Battery Packs that had become over-discharged were sometimes not chargeable in the camera. With Version nnn, such Battery Packs can be charged in the camera."
http://www.canon.co.jp/Imaging/PSG1/PSG1_Firmware-e.html
G2:
http://www.canon.co.jp/Imaging/PSG2/PSG2_Firmware-e.html
Pro90IS:
http://www.canon.co.jp/Imaging/PSPRO90IS/PSPro90IS_Firmware-e.html