Acronis Managed Machine Service fails as soon as network drive is accessed

Hi
This is Acronis B&R 10 Update 5 (Build 10.0.13762) on Windows 2003 R2 Server SP2
I had no problems with Acronis for years but since some days I have a problem with one backup.
I can backup to a NAS without any problem. As soon as I try to change the path of the destination drive to another NAS (where I already have a backup file) the process called "Acronis Managed Machine Service" fails.
I tried with different shares and occationaly I was able to define the backup destination to this path.
After one succesfull backup the same story: as soon as I try to access this share over the GUI (i.e. if I want to look for the size) the same process dies and the Gui is unresponsive.
I can restart the service without any problem but as soon as I use a function that accesses this destination drive the process dies again.
If I change the destination to another system the problem is gone.
The NAS where the problem exists is a Synology with DSM 4.0.
Any ideas?