We don't have any similar problems launching Visual Studio .sln files from Opus, although we've only tried with current versions of Opus. (Opus 10 is very old now.)
From a quick search, the error you're seeing happens if Visual Studio is configured for compatibility with the wrong Windows OS version. That in turn may be happening because you're launching it from Opus and have Opus itself configured in that way, and Windows is inheriting the compatibility settings from the launching process.
I'd suggest turning off all compatibility settings on dopus.exe and devenv.exe.
Also, Opus should not be run as Administrator (unless UAC is turned off system-wide, of course). Opus should be run at the same elevation level as the rest of the desktop it needs to interact with, with elevation then left to the built-in Admin Mode and UAC support in Opus.
(It's also possible the problem you're seeing is something that didn't work in Opus 10 but already works in Opus 12, due to the many changes over the years. If neither suggestion above works or applies, and you're thinking about upgrading anyway, then it may be worth trying the current version to see if the problem is still there.)