Well... You shouldn't "need" to lower/turn off UAC.... It's part of the OS's security... Personally, I hate UAC and turn it off immediately after loading a new OS...but if you want to try it...
Go to...
Control Panel\User Accounts and Family Safety\User Accounts
And click User Account Control Settings and lower the bar...
Another thing you can try is to turn off data execution protection for the Music Sphere .exe...
click the windows button(start)
right-click on computer and select properties...
on the left goto advance system settings
on the advanced tab, click on performance settings...
on the Data Execution Prevention tab
select the bottom radio button and click add
then find the .exe for Music Sphere...
It should be in C:\Program Files\Pioneer\MusicSphere\MusicSphere.exe
or if you're on a 64 bit machine it'l be here...
C:\Program Files (x86)\Pioneer\MusicSphere\MusicSphere.exe
It could also be anti-virus that is killing it as well... try turning all that junk off momentarily...
The only other things I could think to do would be to uninstall ITunes and MSphere and try installing both from fresh downloads...
Also check the event logs to see if there are any related errors...
right-click computer>manage>event viewer>Microsoft logs> and either Applications logs and/or System logs...