I have 2 iMac (one 27" late 2009 and one brand new 27"). Both are running on Mountain Lion and both have Outlook 2011. They are both connected to Exchange Online (part of the 365 services).

Normally, the crashes happens when they are browsing on there Inbox (just clicking on the e-mails to see the preview) or when they want to drag an e-mail on a folder...

On one machine I've try to completely uninstall Office 2011 (following Microsoft procedure http://support.microsoft.com/kb/2398768/) and reinstalling + doing all updates before setting up the account, and it still crach.

Here's some examples:
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Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_BAD_ACCESS
Date/Time: 2013-03-05 14:56:00 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: unknown
Crashed Module Version: unknown
Crashed Module Offset: unknown
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 7
-----
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_BAD_ACCESS
Date/Time: 2013-03-05 15:09:39 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: unknown
Crashed Module Version: unknown
Crashed Module Offset: unknown
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 9
------
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_CRASH (SIGABRT)
Date/Time: 2013-03-05 15:10:57 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: merp
Crashed Module Version: 2.2.4.130117
Crashed Module Offset: 0x00003782
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 7
-------
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_CRASH (SIGABRT)
Date/Time: 2013-03-05 15:11:42 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: merp
Crashed Module Version: 2.2.4.130117
Crashed Module Offset: 0x00003782
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 12
------
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_BAD_ACCESS
Date/Time: 2013-03-05 15:12:02 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: QuartzCore
Crashed Module Version: 304.0
Crashed Module Offset: 0x0016a342
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 12
-----------
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_CRASH (SIGABRT)
Date/Time: 2013-03-05 15:12:21 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: merp
Crashed Module Version: 2.2.4.130117
Crashed Module Offset: 0x00003782
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 12
-------
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_BAD_ACCESS
Date/Time: 2013-03-05 15:12:37 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: unknown
Crashed Module Version: unknown
Crashed Module Offset: unknown
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 11
---------
Microsoft Error Reporting log version: 2.0

Error Signature:
Exception: EXC_BAD_ACCESS
Date/Time: 2013-03-05 15:12:59 +0000
Application Name: Microsoft Outlook
Application Bundle ID: com.microsoft.Outlook
Application Signature: OPIM
Application Version: 14.3.1.130117
Crashed Module Name: unknown
Crashed Module Version: unknown
Crashed Module Offset: unknown
Blame Module Name: PowerPlantCore
Blame Module Version: 14.3.1.130117
Blame Module Offset: 0x00005412
Application LCID: 1033
Extra app info: Reg=en Loc=0x0409
Crashed thread: 11
------

Any ideas?