Magic Mouse clicks twice on dropdowns

Hi, I'm a Mac user since many years, as a software developer with MacBooks and iMacs, and with all of them I've had the same strange behaviour using Magic Mouse 1. When I click on a dropdown selector in Firefox or Safari sometimes it triggers twice. The only way to avoid it is clicking and not releasing the button until I have selected the right item. This does not happens with the integrated trackpad or with the Magic Trackpad, only with Magic Mouse, and in several computers and configurations. I've always thought that it was because a wrong way of clicking, but I've seen other people using their computers with this same problem. I've tried to change the time interval in double click in Accesibility Options but it happens exactly in the same way. Any ideas about how to override this little (but frustrating) issue?