Panasonic have pulled the gh1 v1.2 s/w initial release and uploaded a new v1.2 for download, allegedly the first release didnt have the battery recognition? Anyway, if you need v1.2(why not) and you need 3rd party batteries(why not/cheaper) go here for the windows download, sorry that the mac s/1 didnt seem to get downloaded but maybe somebody else made and ealry discovery on the mac1.2 s/w too. Either way its only an exe file so if you can get to a pc you can do it there too. If you downloaded already from the site and installed, sorry but your stuck.
http://forums.dpreview.com/forums/read.asp?forum=1041&message=33069762
http://forums.dpreview.com/forums/read.asp?forum=1041&message=33069762