How to get the log files
The log files are located in the C:\users\Username\AppData\local\SIX Networks\Play withSIX\logs folder.
The AppData folder might be hidden by default, you can change windows options to make it visible, or you can add \appdata manually in the address bar while in the C:\users\Username folder
Application PAR file (also includes other configuration files):
The par file is located in the C:\users\Username\AppData\roaming\SIX Networks\Play withSIX folder
Game Log Files:
The arma2oa.rpt file, documentated at: http://community.bistudio.com/wiki/RPT
Posting Log Files:
When posting the logs, please make use of one of the following (or similar) services:
As of newer builds you can now enable diagnostics mode for more detailed logging,
and more easily access the log files to send them to us.
Enable diagnostics mode
You should find the Diagnostics menu at the top in the Options -> Settings.
You can enable Diagnostics mode there (restarts the client).
Gathering the log files
Then when the problem occurs, you can again go to the Diagnostics menu and select "Save logs". This should zip up the logs and open the file in Explorer.