FF 27 + Sandboxie + "3rd Party" conflict

The thread in the Sandboxie forum is now on page 9, with minimal official input from the Sandboxie people, and absolutely no input from the FF staff.  And while many have offered strong opinions, there is no definitive conclusion as to what the problem is, nor which program needs to be fixed.

Here is what I believe to be the latest accurate information:

1) FF 27 made a change.  Period.   All other factors remained the same (with the exception of a new Flash Player, which I quickly/carefully ruled-out as being the culprit).

2) The FF 27 change does not directly cripple its functioning in Sandboxie, which is why many users are not impacted by the problem.   However,

3) In the presence of an appropriate third-party program which acts as a "catalyst", the FF+Sandboxie conflict will manifest itself.   [Think of the FF change as somehow "bouncing off" the catalyst, to then "strike at" Sandboxie.   All 3 factors are required here to generate the conflict:  having only two of the three results in an ordinary interaction between those two.]

4) In contrast to my initial report, XP is NOT a factor in this conflict... it can happen on any operating system, and is neither caused nor "enhanced" by running XP.

As for the "catalyst" 3rd-party program, it is highly probable (i.e., almost guaranteed) that one such catalyst is avast 2014 (aka avast 9).   However, it is not the only catalyst (as a few NON-avast users are experiencing the conflict).

We also note that avast 8 is NOT a catalyst.

Until an official fix is released, the conflict is frequently mitigated via a simple work-around:   Setting FF's compatibility tab to "Disable Visual Themes".  

Sandboxie has released a new BETA version, 4.0.9 , which purports to address this issue.   Those wishing to TEST it can download it from http://forums.sandboxie.com/phpBB3/viewforum.php?f=46

Changelog:

1) Incompatibility with FFX 27 and Avast that caused FFX to run with no visible windows.
2) Chrome crash when reporting an issue under Tools->Report an issue...
3) Fixed a problem with DFS drives (Distributed File System)
4) The "InjectDll" setting would sometimes cause DLL initialization to fail with the message "CRT not initialized" or "DLL failed to initialize".

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Comments:

a) Despite being listed as a BETA (testing) version, my preliminary evaluation indicates that it is stable.   While we typically DON'T advocate use of BETA software, anyone who is experiencing one (or more) of the above issues might consider testing this version to see if it fixes things for you.   In particular:

b) It has fixed the issue of FF 27 hanging in Sandboxie for SOME people (e.g., me), but NOT for others (e.g., Hernan).

Reiterating my theory cited above: "In the presence of an appropriate third-party program which acts as a "catalyst", the FF+Sandboxie conflict will manifest itself.   Avast 2014 (aka avast 9) is one such catalyst; however, it is not the only catalyst".

I believe that for those for whom avast was a catalyst, and the only catalyst, this BETA should resolve your issue.   But for those who had a catalyst other than avast (or a second catalyst in addition to avast), you may find that this beta does not resolve your problem.   [I would conjecture that the latter situation --- multiple catalysts --- is what is compounding the problem for Hernan.]