About six months ago, I started having a strange issue where, periodically, Sonar X3E would hang on the Splash Screen when starting up.  This was even before the plugin scan.  The situation was such that I could not stop the process via the task manager (or any other third-party utilities designed to kill orphaned processes) and the only recourse available was to reboot.  However, I always ended up doing a hard shutdown because Windows 7 wouldn't shut down on its own.
 
Rebooting once or twice generally fixed the issue.
 
Last night, the condition happened again.  This time, arbitrarily, I unplugged my CF card reader from the front USB port on my machine.  Instantly, the splash screen went away and Sonar started up - no problems.
 
For whatever reason, it seems that if USB bandwidth has been maximized or exceeded on a particular bus, it causes problems with Sonar - especially in the startup sequence.
 
Just thought I'd post my experience in case anyone else is dealing with this frustration.
 
=HAY

Thanks for that! The computer's USB ports often share a single controller. I installed a separate PCI USB hard to handle the audio interfaces. I don't think USB is quite as bulletproof as we all would like...

 
It's also a resource hog.  When I run a latency monitoring program, the first or second worst offender is the usb handler.  I guess it has to poll continuously for it to track a mouse, but there is certainly a better way that could be used.