MJ Doesn't work if 2 people are logged into the computer

[Planetpapi]

For several months 9 out of 10 times MJ never worked on my PC. I used to restart my computer and then it starts working again. I always get the dial tone but no matter what I entered on the physical phone, the dial tone never cuts off. It will still go on and there are no numbers seen on the soft phone. When it worked, the numbers appear on the soft phone as I dial them from handset.

I have just discovered that If other people logged on to PC with their own account, the above mentioned problem occurs. I guess when I restart only one instance of MJ is active and it works.
Did anyone faced this problem? If so what is the solution? I appreciate your help.
Thanks
Planetpapi