I have also tried the fixed of renaming the dropbox Sync File but to no avail still doesn't work. Maybe something to do with this though as the dropbox folder is just called mSecure not mSecure 5??
Thank you for contacting us, and I'm sorry for the issue you're experiencing. The only thing I can think is that there is some type of corrupted data stored in mSecure, and when a sync is taking place, it's causing a crash. What we need to do first is make sure you're resetting the right data in your Dropbox account. You mentioned seeing a folder named "mSecure", and that's the old folder that was created in previous versions of mSecure. What you'll need to do to locate the "mSecure 5" folder is open your Dropbox account online or open the Dropbox folder on your device. You should see a folder called "Apps." Open that folder, then open the "mSecure 5" folder, then you should be able to open a folder that looks to be named with 10 random characters. Open that folder, and you'll see a file named "data.mssb." Delete that file.
After you delete the "data.mssb" file, open mSecure on either device. Does the file get re-created without the mSecure crashing? If so, delete the file again, then open mSecure on the other device. Does the file get re-created without the mSecure crashing on that device? If the file is re-created on both device, go ahead and open mSecure on both devices to see if the syncing works and then let me know what happens.