How do I change gmail accounts when using the share functionality of an app?

I have 3 gmail accounts coming into my gmail app. I also frequently use the "Share" feature of many apps (Browser, Gallery, BeyondPod...) to share links via gmail however when it opens up the email compose screen sometimes I am given a dropdown to choose which account to send it from and other times it defaults to the account of the last inbox I checked and doesn't give me an option to change it.

This does not seem to have any rhyme or reason to it. Does anyone know how I can make sure to always have the option to choose which account I'm sending from?