I recently had the luxury of trying to figure out why flash10 wasn't working on a 64bit install of scientificlinux 5.3. It had the classic symptom, the plugin is installed, nspluginwrapper is all configured right. None of the packages seemed out of order. I had gone through a few online tutorials about installing 32bit flash on a 64bit workstation with wrapper scripts, ran ldd on the libflashplayer.so file to make sure all the needed libraries were there.

Alas after messing around for a few hours of looking up and googling non-sensical error and warning messages and looking in the wrong places. I decided just for the fun of it to uninstall flash and reinstall it. It then occured to me, was yum installing the needed dependancies? It turned out the flash plugin/player needed 32bit versions of curl for some weird reason (and its dependancies). I wish flash or nspluginwrapper would give more sensible errors!