Same exact problem here. The new flash player installs to about 25% or 30% complete then stalls out and won't finish the installation. I'm also on Yosemite. Now I can't watch videos my friends have posted to Facebook because I'm told my flash player is obsolete. The new flash player won't install and the old one is obsolete and won't work. I had a similar problem to this about a year ago on a different computer with OS 10.6.
Yes, I'm having a similar problem. It starts installing, then the installation window becomes blank.
Apparently you can't download the new flash player if you're running some sort of virus protection software. I temporarily disabled my anti-virus software and was able to download FP without a problem. I just have to trust that Adobe FP does not contain a virus.
There are a few different installers for OS X. Please post a screenshot (https://forums.adobe.com/thread/1070933) of the installer dialog window exhibiting the behaviour to verify which installer is being used.
This morning we resolved a problem that prevented Flash Player installations from completing for some of our Macintosh users.
If you encountered this problem, please delete any previously downloaded Flash Player installer and either:
1.) Download the installer again from https://get.adobe.com/flashplayer
2.) Download the stand-alone installer from http://fpdownload.macromedia.com/pub/flashplayer/latest/help/install_flash_player_osx.dmg