I have been getting a stackoverflow exception in my program which may be originating from a thirdparty libary, microsoft.sharepoint.client.runtime.dll.
The problem you are facing is that the process is 32-bit, but you are running on 64-bit, therefore your dump is a 64-bit dump. To make use of the dump you have to run the following commands:
.load wow64exts
.effmach x86
!analyze -v
The last command should give you a meaningful stack trace.