The icon isn't something from Opus itself. Opus asks Windows, which in turn asks any installed shell extensions, which icon and (optionally) overlay to display for each item, and then displays them.
For some reason, it seems the Sugarsync shell extension may be telling Opus to display that microphone overlay on all the files.
It's possible this is a shell icon caching bug, which happens sometimes and causes the overlay icons to go out of sync. Running Clear Icon Cache may help there. (Opus and Explorer have independent icon caches, so that may explain the difference.)
It's also possible that there are too many shell extensions adding icon overlays on your system. Windows has a hard limit of 15 or so icon overlays, which is very small and easily reached if a lot of shell extensions all add their own overlays (or one extension adds lots). In that case you can end up with different results in different programs because the order the icons are requested determines the winner, and you might do different things in each program to result in a different set of overlays "locked in" until the icon cache is cleared.
A third possibility is there's a bug in the shell extension, which is only triggered when it is run within Opus, or similar. (It's also possible the bug is in Opus, but unlikely in this case, since Opus just asks Windows for the icon and overlay and then displays the result; obtaining and caching the icon and overlay, and talking to any icon shell extensions, are all done by Windows itself.)