My problem:
After installing the andreas00.2col template, the left-sided menu was invisble.
So I replaced the menu code in the template andreas00.2col with the menu code from the minimal template (which came with the default installation)
And now it works!

Original code (left menu did not work):
<div id="avmenu">
<h2 class="hide">Site menu:</h2>
[!DropMenu? &selfAsLink=`1` &useCategoryFolders=`0` &startDoc=`0` &hereClass=`current`!]
<div class="announce">
[and so on..]
Changed code (left menu now works):
<div id="avmenu">
<h2 class="hide">Site menu:</h2>
[[Wayfinder? &startId=`0`]]
<div class="announce">
[and so on..]
I hope I did not break anything else with this hack. Just wanted to share it in case others have the same issue with the menu.
cya,
holger