Occured in version 1.69
What I have done:
1. I wanted to restart my Windows XP and mRemoteNG did not want to exit. So I killed the process.
2. It seems as if I had killed it just at the moment it wrote to my confCons.xml. My connection was broken.
3. The next day I started mRemoteNG and it told me that the connection file is broken and it shuts down itself to prevent dataloss.
The backup file is correct and can be copied over.
The backup file was overwritten with the corrupted file. I am not sure but I think this happened at the second start.
This happened to me two times until now.