I noticed when I put the latest version of my favorite browser (using the latest X-Slacko), one of the strangest things happened. It would ask if I wanted to make it a default browser for various things as it always does-- but the "OK" button would lock, meaning you hadn't selected the value, and when you start up again, it would "forget" your choice.
Since I beat myself up for it repeatedly, I finally gave up and started using Firefox. Well, going back I realized that almost everything in these Mozilla systems can be fixed through their "about:config" pages, and this is no exception.
If you find yourself experiencing this problem, go to about:config and search for "Shell.checkDefaultClient". Double click to switch it to "false". Problem solved.
In case anyone else had that problem and can't live without their Seamonkey and no, I didn't submit a bug report to Mozilla since it seems the Seamonkey devs are fairly stressed out.
EDIT: AND I fixed a toilet today. I am feeling pretty know-how right about now.