do you have any packages or files that are from the stock RO2 files in C:\Users\YourName\Documents\My Games\RedOrchestra2\ROGame\Unpublished?
It happened to me that by mistake I modified a stock RO2 package Props_vegetation and so UDK wanted to save it, which it did but then when I re-opened the map it would crash everytime, I just had to delete the saved file from C:\Users\YourName\Documents\My Games\RedOrchestra2\ROGame\Unpublished and it worked again.
Also you should look at your log file stored in C:\Users\Leo\Documents\My Games\RedOrchestra2\ROGame\Logs to see if there is any useful information