Hello,
This error usually indicates that the "symsnap.sys" driver is not properly registered. The BESR install process registers this driver file, but we've seen rare cases where the registration process fails for some reason. This error is one symptom of that problem.
I know that the BESR 7.0 product includes a batch file that re-registers this driver. If I remember correctly, the batch file is named something like "fixinstall.bat" and is placed on the hard drive during installation. Try running this batch file and then try to capture an image again. I do not believe a reboot is required after running the batch file (I could be wrong).
For earlier versions of the product (BESR 6.0, LSR 6.0/3.0) a similar batch file is likely availble from Symantec support, and may even be available via a knowledge base document.
Thanks.