I have some good news about this issue : it seems a solution exists
Let me tell you how I proceded :
Having spent some time on Dojo forums, I suspected something with Firebug extension, or with Dojo Firebug extension (some Firefox crash issues were reported about these extensions when using dojo).
1) I first tested on FireFox, on Project'Or RIA V2.4, with a Big (very big) database :
- 1000 projects,
- 10000 activities,
- 500 resources,
- about 30 assignements to activities per resource.
I tested on Firefox, but could not have it crash (but now I'm not sure any more to have executed the "dangerous" sequence).
2) Then I installed Firebug extension and tested again : after fews tests, I had a FF crash

.
So I could produce the issue !

I tried to determine a test sequence to reproduce the crash, and found one easy :
- open Project'Or RIA,
- select real work allocation (all is OK to now

),
- select project list (

),
- select real work allocation again : crash

.
This sequence is systematically leading to FF crash.
3) I deactivated Firebug extension, and tested again:
- real work : OK

- project list : OK

- real work : OK

- project list : OK

- real work : CRASH

So I got the crash, but later.
I had several tests, with firebug deactivated, crash is randomly apearing and relatively frequent, but much less than when it is activated.
4) Then I decided to uninstall Firebug extension and test again.
Test = crashing again, the same way it crashed with the extension installed but deactivated.
5) So I got back to Dojo and installed new Dojo 1.8 on ongoing V2.5.
- real work : OK

- project list : OK

- real work : OK

- project list : OK

- real work : OK

- and continued more than 10 times without any issue
6) Facing this good improvement, I got to silly test : I reinstalled Firebug, activated it, and tested again.
I could not reproduce the crash.
I tested for some time, withouit any issue, even if I activate Firebug UI.
So I think Dojo 1.8 fixes some issue with FireFox, even if I could not find explicit fixing described in the Dojo bug tracker.
I will deploy V2.5 with Dojo 1.8 soon.
The V2.5 developments are late, so I will report all the functional upgrades planned on this version to another version to have a quick deployment of this fixing.
I first have to spend some time on testing as new Dojo version often brings few regressions.
This will make this version a pure technical improvement.