Problems arise when you have multiple browsers and they fight to be your preferred one. In a coworker's box, it tries to open konqueror (WTF?!).
One way to fix the issue is changing browse-url-browser-function.
(setq browse-url-browser-function 'browse-url-generic
Not only that, but the nice thing would be that emacs reused a browser if you have one opened (firefox or chrome) and opened a new one (chrome) otherwise.
I've been messing a bit with proced.el to find out how to list external processes programmatically, but had no luck. If I find out how, I 'll modify this post with new info.
If you have related info, please, comment :)
Thanks to Davazp that pointed me to list-system-processes function, I just wrote the code to use an already opened browser to open a given url.
A good quickreference to look for function signature differences between elisp, scheme and cl is here. It helps quite a lot