Update: This solution doesn’t really work. Prism doesn’t start up without a network. So if you are offline, you don’t get to see anything. If you are online (connected to a network) though it works. I will update this post if I find a solution.
Here are the instructions to get Gmail Offline working with Prism on a 64 bit installation of Ubuntu 9.04. I am assuming you have already installed the package prism-google-mail. If not, go to Synaptic Package Manager and install it.
1. Download the 64 bit version of Google Gears found here. (There are 3 links; I used the last one : gears-linux-opt-05210.xpi). Download it with another browser like Opera, so that the install dialog does not pop up.
2. Open the downloaded XPI file with the Archive Manager (File roller). (It’s just a matter of right clicking and extract. )
3. Edit the install.rdf fil. Search for code that looks like :
and replace it with this :
4. Save the file. Archive Manager will asking you whether you want to update the archive. Say Yes.
5. Open Prism – Google Mail and on the bottom right corner click the Settings button and navigate to Tools > Addons.
6. Drag and drop the modified XPI file into the Addons window.
7. That’s it.