WordPress Plugin update loop

I create a simple plugin and added it to the WordPress SVN. I added and activated it on one of my client's website. The plugin works fine but has the message

There is a new version of WP-Admin Distribution List available

Keeps poppping even after I updated the plugin using the 'update now' button

My guess is that the copy of WordPress on my client's server is not updating the database with the new info. Can someone tell em what am I missing?
Here's the Plugin

via Chebli Mohamed