By now, everyone should probably know Steve Job was right: Adobe Flash Player is garbage, not only because is has plenty of security holes, but also because is an inefficient way of making the CPU display videos.
And, yes, supposedly, they are trying to close the security holes, as every two weeks or so a new version is released.
But then, that leads us to realize that Adobe's servers entrust to provide the installers are also just a piece of garbage.
Yes, I'm upset, because I'm charged to keep the computers where I work safe, which means updated. But if I don't use alternative download methods it is impossible to download the 14Mb installer via the on-line Flash installer, because it is damm slow and because the Flash installer will most certainly give a "download error" when progress is between 13%-26%.
The solution (#1 - if you want to keep Firefox with Flash enable) is to find alternative off-line installers and download it using download managers (such as DownThemAll) that could pause and resume the download process.
The other solution (#2 - Chorme) is to just uninstall any Flash from Firefox an rely solely on Chrome's auto update to brings you the last version of the Flash Player. Which, of course, is not 100% sure, because that leaves on the user's hand the ability to install whatever version (and sourced) version of the Flash Player.