update manager in kubuntu reported bug

[Lukáš]

There were no usual updates displayed on my computer. I tried to update manually. Program started as usual, but during loading it showed this warning
in czech:

Nelze zjistit informace o balíčku
Během sbírání informací o balíčku nastal neřešitelný problém.
Nahlaste prosím tento problém vůči balíčku „update-manager“ a přiložte následující chybovou hlášku:
'E:Otevírám /etc/apt/sources.list.d/playonlinux.list - ifstream::ifstream (13: Operace zamítnuta)'

in english translation:

It's not possible to find out information about the package.
During loading information about this package has happened insoluble problem.
Please report this problem towards the package "update manager" and attach this error report :
'E:opening /etc/apt/sources.list.d/playonlinux.list - ifstream::ifstream (13: Operation denied)'

I installed play on linux about two months ago. I added new repository to upgrade this programe. I don't know where is the problem.