Hi - we here in the forum need a bunch of information on your system specifications, and some settings and such, prior to being able to help you figure this out.
SOOOO, please review and respond to each of the following:
1. Are you running 32-bit or 64-bit Windows?
2. Is your version of Windows up to current maintenance levels?
3. What precise version of X1 are you running? (If you click on Help>About Sonar, it will open up a display window with information on the version and build number of your Sonar installation, as well as whether or not it is a 32-bit or 64-bit installed version. You can close that window after noting the above info, which you can then post back to this thread - along with your responses to the other things I am asking for). Please note that X1 has multiple maintenance versions, with X1d being the most current of those.
4. You should look in Task Manager after shutting down Sonar, and see if it is somehow still running - (it would show as SONARPDR.exe).
There are a BUNCH of past threads for this very same issue, and it would appear that many folks end up having to reboot to get it straightened out.
Anyways, here are some of the threads:
http://forum.cakewalk.com/tm.aspx?m=2436572
http://forum.cakewalk.com/tm.aspx?m=2077449
http://forum.cakewalk.com/tm.aspx?high=&m=939514&mpage=1#939535 Bob Bone