We need more info to investigate.
Which build ? 32 or 64bit?
Crashlog ?

Jens

I try this two versions:
blender-2.61-release-OSX_10.5_i386
blender-2.61-release-OSX_10.6_x86_64
It's the same when I want to open: I have the same message: Blender a quitté de manière imprévue. Cliquer sur Relancer pour rouvrir l'application. Cliquez sur signaler pour obtenir plus de détails et envoyer un rapport à Apple. (sorry, message in french because I'm french)

I go to my message console to see what happen: (In Utility folder, console) for 32 bits version
30/12/11 04:09:51 ReportCrash[12740] Saved crash report for blender[12737] version 2.61 (2.61, 2011-Dec-13, Blender Foundation) to /Users/eve/Library/Logs/DiagnosticReports/blender_2011-12-30-040951_iMac-Eve.crash
30/12/11 04:12:52 [0x0-0x14f14f].org.blenderfoundation.blender[12764] Fatal Python error: Py_Initialize: unable to load the file system codec
30/12/11 04:12:52 [0x0-0x14f14f].org.blenderfoundation.blender[12764] ndof: 3Dx driver not found
30/12/11 04:12:52 [0x0-0x14f14f].org.blenderfoundation.blender[12764] found bundled python: /Applications/Blender 2.6.1 (32 bits) 24:12:11/blender-2.61-release-OSX_10.5_i386/blender.app/Contents/MacOS/2.61/python
30/12/11 04:12:52 [0x0-0x14f14f].org.blenderfoundation.blender[12764] Warning : Blender application is located in a path containing : or / chars
30/12/11 04:12:52 [0x0-0x14f14f].org.blenderfoundation.blender[12764] This may make python import function fail
30/12/11 04:12:52 [0x0-0x14f14f].org.blenderfoundation.blender[12764] LookupError: no codec search functions registered: can't find encoding
30/12/11 04:12:55 com.apple.launchd.peruser.501[114] ([0x0-0x14f14f].org.blenderfoundation.blender[12764]) Job appears to have crashed: Abort trap
30/12/11 04:12:55 ReportCrash[12767] Saved crash report for blender[12764] version 2.61 (2.61, 2011-Dec-13, Blender Foundation) to /Users/eve/Library/Logs/DiagnosticReports/blender_2011-12-30-041255_iMac-Eve.crash

for 64 bits version:
30/12/11 04:13:32 [0x0-0x20020].com.vmware.fusion[227] 2011-12-30 04:13:32 CUPS config timestamp change detected but old config retrieved via interface!
30/12/11 04:16:49 [0x0-0x151151].org.blenderfoundation.blender[12794] Fatal Python error: Py_Initialize: unable to load the file system codec
30/12/11 04:16:49 [0x0-0x151151].org.blenderfoundation.blender[12794] ndof: 3Dx driver not found
30/12/11 04:16:49 [0x0-0x151151].org.blenderfoundation.blender[12794] found bundled python: /Applications/Blender 2.6.1 (64 bits)(22:12:2011) /blender-2.61-release-OSX_10.6_x86_64/blender.app/Contents/MacOS/2.61/python
30/12/11 04:16:49 [0x0-0x151151].org.blenderfoundation.blender[12794] Warning : Blender application is located in a path containing : or / chars
30/12/11 04:16:49 [0x0-0x151151].org.blenderfoundation.blender[12794] This may make python import function fail
30/12/11 04:16:49 [0x0-0x151151].org.blenderfoundation.blender[12794] LookupError: no codec search functions registered: can't find encoding
30/12/11 04:16:51 com.apple.launchd.peruser.501[114] ([0x0-0x151151].org.blenderfoundation.blender[12794]) Job appears to have crashed: Abort trap
30/12/11 04:16:51 ReportCrash[12797] Saved crash report for blender[12794] version 2.61 (2.61, 2011-Dec-13, Blender Foundation) to /Users/eve/Library/Logs/DiagnosticReports/blender_2011-12-30-041651_iMac-Eve.crash

oups! I'm so stupid!!!!! I found my fatal error!
I did not understand why in the console, in the launching of Blender, it did not find "Python"... I searched so for my part during all night an answer to this question.
Do not laugh at my explanation...
I had simply create a file in my file " Applications " and put Blender indoors... I took it out from this file and put the file Blender downloaded directly in the file " Applications "... And it's ok now!
There is therefore no bug of Blender 2.61, but my human error!
I apologize for having believed in a bug of Blender 2.61
Thank you nevertheless to have taken my request in consideration and answered it so quickly. Thanks again. I hasten to test Blender 2.61 (I add that I am in my touts at the beginning in the field of the 3D)
Sorry for my very bad english, I'm french.
With still all my gratitude and my salutations

Hey, np, iám glad it turned out this way. Was starting to think we have a localization problem :)

Have fun then, i´ll close this entry now.

Jens