X2 Reference Guide says,
"Previous versions of SONAR required a user to have Windows Administrator status. This is no longer the case. Any level of user can now install and run SONAR." Maybe this made the OP (and me certainly) think that it's not necessary to "run Sonar as administrator."
Also, as I suggested earlier, Edirol synths are no longer supported (Vista was the last compatible OS). I used to use Edirol Orchestra, but I believe there wasn't a VST version.