Cheers. That's similar to how it's now (hopefully) been fixed.
I raised an incident with Symantec and the advice received was...
1. Uninstall
2. Run a remove batch script to expunge all traces of BESR v7
3. Run a utility to remove any remainders of Live State Recovery v6
4. Reinstall
(script & utils supplied by them)
This still failed on the symsnap.sys install. Killed the msiexec, logged out and back in, and "completed" install.
Symantec then advised this:
1. Copy Symsnap.sys, V2iMount.sys, VProEventMonitor.sys and wimfltr.sys from C:\Program Files\Symantec\Backup Exec System Recovery\Shared\drivers\win32\win32\ to C:\Windows\system32\drivers\
2. Run FIXINSTALL.BAT from C:\Program Files\Symantec\Backup Exec System Recovery\
3. Reboot the system
After doing this, I've successfully taken an image.
For info, when I was installing on this server, I didn't uninstall LSR first. The BESR installer detected it and did the uninstall, rebooted, then carried on. I had another server to upgrade and on that one I uninstalled LSR first, rebooted and then installed BESR and it worked with no problems.