SD 7.6 restore fails on Windows 2008 R2

I implemented SD+ several times during the last three years with no issues. This time I decided to build a fresh Windows 2008 R2 server for SD+. The installation went OK but when I tried to restore a backup file it failed with "Access Denied" error.

Here is the configuration:
Server Hardware: HP Proliant DL120 G6, 8GB memory and two 250GB SATA drives in a mirror set.
OS: Windows 2008 R2 (which is 64 bit).
SD+ Enterprise 7.6
Old Installation: SD+ Enterprise 7.6 on Windows XP SP3 (still within the 30 days trial but purchased the licence two days ago).

This is the first time I encounter an error with RestoreData.bat.

Any ideas?
Is SD+ recommended on 64 bit OS platforms?