I encountered the problem again. I get the Problem signature:
Problem Event Name: BEX
Application Name: plugin-container.exe
Application Version: 13.0.0.4535
Application Timestamp: 4fc8de63
Fault Module Name: NPSWF32_11_3_300_257.dll_unloaded
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 4fc821fc
Exception Offset: 54e59903
Exception Code: c0000005
Exception Data: 00000008
OS Version: 6.1.7601.2.1.0.256.48
Locale ID: 1033
Additional Information 1: 0a9e
Additional Information 2: 0a9e372d3b4ad19135b953a78882e789
Additional Information 3: 0a9e
Additional Information 4: 0a9e372d3b4ad19135b953a78882e789

I am not smart enough to determine if it is a FF problem, a Flash problem, or a Sandboxie problem. But, I bet someone on here can point me in the right direction for a fix.

I have not tried, yet, to disable protected mode in Flash as this problem only happens occasionally.

I had the issue of plugin container not working a few more times so I allowed flashplayerplugin 11_3_300_257.exe access to the internet. Curiously, I don't recall being asked if it wanted access but perhaps it did notify me and I ignored it. I am going to see how that works, without having to disable protected mode in Flash. I've had a few other issues since upgrading the Flash plugin. Hopefully now that it has internet access things will work OK

neither nor.

i have now the normal installation on two systems win7/32+64 left behind and it works. just running fx13 in sandbox and watching youtube - no issues (64bit sandboxed outstanding, can not test same time)

major hint is

ok, this looks much nicer


may possible. i cannot check that out now.

#
no issues with firefox 13, latest flash 32bit and sandboxie 3.70 - youtube tested

must be something on your computer.

I finally disabled Flash Protected Mode as suggested in several posts here and, so far at least, I have not encountered the problem of the plugin container stopping. W7, FF 13, 32bit. I assume this will all get sorted out in the wash in the next several days or weeks.

as i wrote there are issues with your system - your problems are not in general!

It's also possible to store a modified copy of the file "mms.cfg" someplace on your hard drive - a copy that includes the "ProtectedMode=0" setting - and then use Sandboxie's AutoExec command to copy that file into the sandbox as soon as the sandbox is first used.

When sandboxed Firefox runs, and Flash uses the settings in the modified file, Protected Mode will be turned off.
Sandboxie will be your protection.

When unsandboxed Firefox runs, Protected Mode will still be in effect because the unmodified "mms.cfg" file will be used.

For me, copying the file into the sandbox seems to add about 1 more second, before the sandboxed Firefox window opens.

That solution was already linked
http://sandboxie.com/phpbb/viewtopic.php?p=81042#81042

btw - how many of you use avast AND windows firewall and have this issue?

otherwise please name your software, if you have issues.

Not exactly certain what you mean that my problems are "not in general" there are issues with my system. It worked fine until I installed the new version of flash and then I got the error message re plugin container. Now that I have disabled flash protected mode, problem is solved. BTW, I use the free version of Avast! and Comodo firewall and the link you posted in your last post is dead.

i see no reason why not change ProtectedMode=0 , since we already got SB protection

Sounds similar to the printing problem when Acrobat Reader is sandboxed where I have had to turn off protected mode.

my firefox 13 hangs completely when there is some flash content on a page. the new flash player doesn't have permission to run.
This never happended with the older flash versions.

this issue was solved long ago from tzuk - if you still have that problem its also your system.

people - uninstall flash complete, then clean up and reinstall from scratch.
http://www.adobe.com/products/flashplayer/distribution3.html (plugin based for firefox)

uninstaller/cleaner
http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html

delete flash folders

Windows XP/2000:
► C:\Documents and Settings\<username>\AppData\Adobe\Flash Player
► C:\Documents and Settings\<username>\AppData\Macromedia\Flash Player

Windows 7/Vista:
► C:\Users\<username>\AppData\Roaming\Adobe\Flash Player
► C:\Users\<username>\AppData\Roaming\Macromedia\Flash Player

reinstall.

btw if you have issues outside sandboxie dont post here please, check out mozillazine
http://forums.mozillazine.org/

if it works outside it works inside!

in my case like i wrote its happen ONLY inside SB (firefox) outside all run normal


EDIT

@ Brummelchen

your solution doesn't work , same laggy playing under SB

EDIT 2

since this issue ONLY happen under sb in firefox , its a firefox or/and SB matter , under chrome this problem doesn't exist

Well, I finally broke down and tired the fix suggested by Brummelchen, i.e., uninstall and reinstall.

I found a few extra minutes and, even though the problem had disappeared with flash protected mode turned off, I thought I should investigate.

So, I used the uninstaller from Adobe's website and manually removed the suggested folders, re-started, and reinstalled. I should mention I also turned off advanced protection in Comodo and my anti-virus before I uninstalled/reinstalled.

The newer Flash with protected mode now works in sandboxed FF13! I should also note that the problem I had with a few websites not immediately displaying flash content until hit with the mouse has also been fixed. Although my machine is less than 2 years old, I update flash whenever necessary. For whatever reason, old code hanging around from the various versions of Flash seems to have been the problem.