Alex,
Version 10.5 does NOT support Windows 2008. The 10.5 Version is only available for 32bit OS's
It was never tested or expected to run on Windows 2008. I know this because I worked at Vontu/Symantec for 7 Years.
You should really be using a 64bit OS for everything for WHEN you get to DLP 12.0 it ONLY supports 64bit OS's.
Honestly you should be upgrading to V11.x or to DLP 12.0 at this point. DLP 10.x is soo old and anitquatied that there are so many improvements that you are missing.
Hope this makes sense.
If this solves your questions please marked as solved.
Ronak