I am creating a table in which I have cells containing itemize environments. For a given row I have either zero or two cells containing this environment and working together. However the text for the items of the first cell is usually longer than the text for the items of the second cell.
I am looking for a way to implement this table with the bullet points of the items being respectively at the same height. A picture being better than a long description, here it is:

I would like the bullet point of Short 1 to be at the same level as the one from the first long item, and the same goes for Short 2 and its related item.
Here is the code used to produce this table:
\documentclass{article}
\usepackage{enumitem}
\usepackage{array}
\begin{document}
\begin{table}[H]
\begin{center}
\begin{tabular}{| m{0.3cm} | m{5.5cm} | m{4cm} | m{1.8cm} | m{1cm}|}
\hline
1 &
\begin{itemize}[leftmargin=0.3cm]\itemsep0pt
\item This is a first long long long item, spanning on two lines
\item And here comes a second one lon long item
\end{itemize} & Some text which can be either long or short, there is no general rule &
\begin{itemize}[leftmargin=0.3cm]\itemsep0pt
\item Short 1
\item Short 2
\end{itemize} & Some short text\\ \hline
\end{tabular}
\end{center}
\end{table}
\end{document}
NOTE 1 I would like a solution as compact in height as possible
NOTE 2 I am using the m{<value>} column style because the longest cell for a different rows is not always the same.
NOTE 3 I am aware that the Table is ugly and the vertical lines should be removed to match more to a more readable and reader-friendly solution but this is a mandatory template... Too bad...
EDIT Trylks proposed to use a combination of \multirow in the non-list cell and to split the list cells in more cells. This does fix the problem of the vertical alignment of the items but it also creates misalignments for the other cells.
MWE for the Edit suggestion
\documentclass{article}
\usepackage{enumitem}
\usepackage{array}
\usepackage{multirow}
\begin{document}
\begin{table}[H]
\begin{center}
\begin{tabular}{| m{0.3cm} | m{5.5cm} | m{4cm} | m{1.8cm} | m{1cm}|}
\hline
\multirow{2}{*}{1} &
\begin{itemize}[leftmargin=0.3cm]
\item This is a first long long long item, spanning on two lines
\end{itemize}
& \multirow{2}{*}{Some text which can be either long or short, there is no general rule} &
\begin{itemize}[leftmargin=0.3cm]\itemsep0pt
\item Short 1
\end{itemize}
& \multirow{2}{*}{Some short text}\\
& \begin{itemize}[leftmargin=0.3cm]
\item And here comes a second one lon long item
\end{itemize}
& &
\begin{itemize}[leftmargin=0.3cm]
\item Short 2
\end{itemize}
& \\ \hline
\end{tabular}
\end{center}
\end{table}
\end{document}
And the corresponding output:

EDIT 2 jfbu proposed a solution which seems to work (see his answer) for the above case but it is just a coincidence. If one item has a text longer than two lines, it crashes also. See the MWE and its output:
\documentclass{article}
\usepackage{enumitem}
\usepackage{array}
\begin{document}
\begin{table}[H]
\begin{center}
\begin{tabular}{| m{0.3cm} | m{5.5cm} | m{4cm} | m{1.8cm} | m{1cm}|}
\hline
1 &
\begin{itemize}[leftmargin=0.3cm]\itemsep0pt
\item \strut This is a first long long long item, spanning on two lines. This is a first long long long item, spanning on two lines. This is a first long long long item, spanning on two lines \strut
\item \strut And here comes a second one lon long item \strut
\end{itemize} & Some text which can be either long or short, there is no general rule &
\begin{itemize}[leftmargin=0.3cm]\itemsep0pt
\item \strut Short 1 \hfill\break \strut
\item \strut Short 2 \hfill\break \strut
\end{itemize} & Some short text\\ \hline
\end{tabular}
\end{center}
\end{table}
\end{document}



\multirow. They are vertically centered any more and for the one in the middle (the long text), it does not break the line when required and overlays the cell next to it. – Ludovic C. Oct 04 '13 at 11:01