Bug 796834

Try to run firefox with clean profile and in safe mode (with extensions disabled)
by firefox -safe-mode.

This also might be related to hardware acceleration, try turning it off by:
Edit/Preferences/Advanced/General/Browsing/Use hardware acceleration when available.

You also don't need to use nspluginwrapper while Firefox is now using plugin container which works fine with x86_64 adobe flash plugin. So try to remove it.

Also show us output of:
ls /usr/lib64/mozilla/plugins/
ls /usr/lib/mozilla/plugins/
rpm -q xulrunner firefox flash-plugin

Thanks for the feedback. I could not reply as flash worked for a while again. Now is running too fast after I initialised the cache and waited for a couple of days. 

Tried your suggestions. No effect on problem. 

So here is the data you requested:

ls /usr/lib64/mozilla/plugins/
libflashplayer.so
libgnashplugin.so
libgnome-shell-browser-plugin.so
libjavaplugin.so
liblightsparkplugin.so

ls /usr/lib/mozilla/plugins/
no output

rpm -q xulrunner firefox flash-plugin
xulrunner-10.0-1.fc16.x86_64
firefox-10.0-2.fc16.x86_64
flash-plugin-11.1.102.55-release.x86_64

Good luck to solve it.

This has been affecting Fedora 15 as well.  After the recent firefox update Pandora regularly crashes firefox for me, and this appears on the console:

 Gdk-ERROR **: The program 'npviewer.bin' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
  (Details: serial 1091 error_code 8 request_code 142 minor_code 3)
  (Note to programmers: normally, X errors are reported asynchronously;
   that is, you will receive the error a while after causing it.
   To debug your program, run it with the --sync command line
   option to change this behavior. You can then get a meaningful
   backtrace from your debugger if you break on the gdk_x_error() function.)
aborting...
*** NSPlugin Wrapper *** ERROR: NPP_HandleEvent() wait for reply: Connection closed
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2219):invoke_NPP_SetWindow: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** ERROR: NPObject proxy 0x7f2c5d81f600 is no longer valid!
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))
*** NSPlugin Wrapper *** WARNING:(../src/npw-wrapper.c:2848):invoke_NPP_HandleEvent: assertion failed: (rpc_method_invoke_possible(plugin->connection))

You seems to have free Flash implementation gnash and lightspark installed. They could collide with adobe's flash plugin. Try to uninstall them:
yum remove gnash lightspark lightspark-mozilla-plugin

My problems seem to have gone away when I uninstalled nspluginwrapper.  I don't think I ever had gnash lightspark or lightspark-mozilla-plugin

(In reply to comment #5)
> My problems seem to have gone away when I uninstalled nspluginwrapper.  I don't
> think I ever had gnash lightspark or lightspark-mozilla-plugin

Sorry, I was referring to DM message.

Uninstalling nspluginwrapper fixed it for me as well.

Same here. Had to remove nspluginwrapper to get flash to behave nicely.

yum remove nspluginwrapper

I believe I have had the same problem on F15.  After reading the comments on this bug report, I removed nspluginwrapper and everything works great now.  Before, many flash apps such as the CNN video player and the charts on mint.com would crash almost as soon as they loaded (becoming unresponsive, sometimes going blank).  Now they work.  Someone should probably update the ubiquitous "how to install flash on fedora" documentation.

Yes, don't use nspluginwrapper unless you have to.