Unable to Launch Selected pcAnywhere Host

We recently had all our people install Windows 7 and pcAnywhere. As awesome as that is, many of us experienced an error like this: "Unable to launch the selected pcAnywhere host because another pcAnywhere host is running". Although after we got rid of the error, everything went back to normal, but It would be great if any of you can explain why it was there in the first place. Have a great day and thanks a bunch.
