I just downloaded install_flash_player_13_active_x.msi and install_flash_player_13_plugin.msi - both are version 188.8.131.529; the timestamp is April 25, same as the exe installers.
Make sure you don't have any old version cached on some corporate server.
We are looking into this. There are a few other threads on this same issue. Please see:
I'll be posting updates on the other threads. Please follow one of those two threads.