Wow, really Adobe Flash Player installer?
I decided to install the Flash 10.1 RC this morning on Snow Leopard. I pre-emptively quit Safari and all my other apps in preparation for this installation (since I often test pre-release software). To my knowledge, no other apps were running — least of all any that would be using Flash.
To my surprise, I received a call from Adobe about this issue and we worked to recreate it, but I was unable to. Could be a fluke — but at least Adobe was rather responsive in looking into this!