I am also unable to reproduce the error message you say you're getting. At any rate, I'd like to suggest that get rid of the \cline instruction and modify your table to give it a much more open look, by (a) getting rid of all vertical lines, (b) getting rid of most of the horizontal lines generated by \hline, and (c) using the macros \toprule, \midrule, and \bottomrule of the booktabs package for the remaining horizontal lines.
Moreover, in order to give the table a fighting chance to fit insde the text block, I would further like to suggest that you use a tabularx environment with an overall width of \textwidth and use automatic line wrapping for three of the six data columns.
A final comment: What might be the purpose of boldfacing all entries in the final column?

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[a4paper,margin=2.5cm]{geometry} % set page size parameters
\usepackage{tabularx,ragged2e,booktabs}
% define a centered version of the "X" column type
\newcolumntype{C}{>{\Centering\arraybackslash}X}
\usepackage[skip=0.5\baselineskip]{caption}
\begin{document}
\begin{table}[h]
\caption{My caption}
\label{my-label}
\begin{tabularx}{\textwidth}{@{} l CcCCcc @{}}
\toprule
& Windows Forms & PDF & Windows Forms\slash GDI+ &
Windows Media Player & Direct3D & \textbf{WPF} \\
\midrule
Grafické rozhranie & X & & & & & \textbf{X} \\
Dokumenty na obrazovke & X & & & & & \textbf{X} \\
Dokumenty s pevným, formátom & & X & & & & \textbf{X} \\
Obrázky & & & X & & & \textbf{X} \\
Video a zvuk & & & & X & & \textbf{X} \\
2D grafika & & & X & & & \textbf{X} \\
3D grafika & & & & & X & \textbf{X} \\
\bottomrule
\end{tabularx}
\end{table}
\end{document}
Postscript: Happily, this code is compatible with the babel package and the use of either the czech or the slovak language option.
\documentclass{article}\begin{document}\end{document}compiles without issue for me... although the table doesn't fit the page at all. – BMWurm Dec 07 '15 at 19:38\cline{2-7}it is working ... but with this nope – Tomas Dec 07 '15 at 20:37\usepackage[czech]{babel}or\usepackage[slovak]{babel}, can you confirm? – egreg Dec 07 '15 at 20:49