Firefox Flash plugin crashes when FF launched with "Run as different user"

Question

I often start Firefox in Windows 7 (x64) using the "Run as different user" mechanism. After upgrading my Flash plugin to v11 (11.8.800.94), the browser will hang for several minutes when visiting any page that contains Flash content. When Firefox becomes responsive again, scrolling a page with Flash content will cause the app to hang again. Disabling the Flash plugin eliminates the problem.
It seems the plugin is silently crashing -- I'm not alerted to a plugin crash in any way (no dialog or yellow "Flash player crashed" notice at the top of the window), but after FF hangs I will see a new crash report entry in the FF about:crashes list. An example crash report is available at https://crash-stats.mozilla.com/report/index/ff452291-b5b2-44e4-a172-416792130818
The plugin does not crash when Firefox is running under the same account that is logged onto Windows interactively -- only when running FF as a different user. For example, if I log onto Windows with user account Adam and launch FF normally, the problem does not exist. If I close FF and launch it as user Bob (shift+right-click Firefox Shortcut, choose "Run as different user"), the problem will appear. However, if I log into Windows as user Bob and launch FF normally, the problem does not exist.
I have tried the following as troubleshooting steps, all to no effect:
Create new Windows user accounts to rule out potential Windows or Firefox profile issues.
Use another PC (also Windows 7 x64). The same behavior occurs on both PCs
Disable AVG antivirus.
Upgrade Firefox to latest version (23.0.1).
Disable Flash hardware acceleration.
Give both user accounts full local admin privileges.
Can anyone suggest something to try next?
Update: Per the troubleshooting instructions at < http://forums.adobe.com/thread/1018071?tstart=0 >, I was able to eliminate the problem by adding the line
ProtectedMode=0
to my C:\Windows\SysWOW64\Macromed\Flash\mms.cfg file to disable Flash Player Protected Mode. There are instructions on that page for submitting a Protected Mode-related bug, and I will follow through with that.

Answer 1

Maybe you did't understand my previous statement. There are no crashes in FF 3.6, There is no previous evidence FF 14 was ever here, I completely uninstalled all trace of Firefox, no app data, no preferences, no cache. I will upgrade to FF14 so I can send IDs,
so here ya go.
Crash ID: bp-fa9da320-92dc-47f7-afff-33e702120718
AdapterDeviceID: 0x2a02
AdapterVendorID: 0x8086
Add-ons: {972ce4c6-7e08-4474-a285-3208198ce6fd}:14.0.1
BuildID: 20120713134347
CrashTime: 1342655269
EMCheckCompatibility: true
Email: [email protected]
FramePoisonBase: 7ffffffff0dea000
FramePoisonSize: 4096
InstallTime: 1342655256
Notes: AdapterVendorID: 0x8086, AdapterDeviceID: 0x2a02GL Context? GL Context+ GL Layers? GL Layers+
ProductID: {ec8030f7-c20a-464f-9b0e-13a3a9e97384}
ProductName: Firefox
ReleaseChannel: release
StartupTime: 1342655256
Theme: classic/1.0
Throttleable: 1
URL: http://www.mozilla.org/en-US/firefox/14.0.1/whatsnew/?oldversion=rv:1.9.2.13
Vendor: Mozilla
Version: 14.0.1
This report also contains technical information about the state of the application when it crashed.