In an effort to help folks that are running into installer errors I have decided to package up a manual installer option for iPhoto2Gmail. Please be sure to carefully follow the instructions in the ReadMe file. This is the best solution I can think of since I have not been able to reproduce the problems that some users have told me about. Download it Here
Please note: the normal installer linked on the sidebar is still the preferred method of getting the plugin!
I have also updated the iPhoto2Gmail uninstaller -- it's a bit prettier and should do a better job of removing old versions or failed installs.