muon package manager thinks that other package manager is open, and is not

Solution 1:

I solved it. I made the upgrade of all packages with sudo apt-get upgrade inside Terminal (Konsole), it donwloaded the packages, installed them, and configured them. After that upgrade muon (package manager and software center) is capable to install and remove packages, nevertheless I need to see if this issue repeats again, but for now this question is solved. Thanks.

That upgrade of 202 packages was the upgrade of KDE platform version 4.7.3 to 4.7.4.

Solution 2:

After closing Muon you should verify that no apt and dpkg processes are still running. In a terminal, enter ps -efl | egrep 'apt|dpkg' to list possible suspects. then use kill -9 nnnn to stop them and try running apt-get again.

UPDATE

If this doesn't help, you should check if there is a lock file in one of the directories Muon accesses.

Check /var/lib/dpkg/lock, then look in the /var/cache/apt/archives/ directory, ...

Solution 3:

Your problem seems to be described here. Please try the advice in comment#1.