I did start my computer this morning, then went into the Task Manager\Processes to see if there were any instances of SODE running, but there was nothing relating to SODE. I then loaded P3D and everything worked okay, no boxes popping up telling me there were multiple SODE processes running.
Then the problem, as I suspected, didn't had anything to do with either GSX or the SODE installation but, it was simply caused by a previous version of SODE not closing from the last session of the sim, which might happen if the sim crashes abruptly.
I have another problem now regarding FSX. Since I installed the latest version of GSX Ground Services, every time I try to start FSX, a box pops up stating that FSX has stopped working. I have tried to load FSX several times this morning and each time the same problem occurs (please see attached screen print).
Have you any idea what may be causing this massive problem?
Your screenshot is not very useful and no, I don't think it has anything to do with GSX. Maybe it's possible you have a wrong registry keys for the compatibility, which is set automatically by Windows, and prevents FSX from starting.
Try running the FSDT Live Update, because it will clear up that key, and hopefully the sim will start again.
If it doesn't, you should check the Windows Application log in the Event Viewer utility, which should give more details about the error.