I can select vertices by using "b" for Box Select, but I'm unable to click a single vertex by a right-click or left-click.
When I right-click a vertex, the mouse pointer switches to another location instead.
When I left-click a vertex, nothing happens at all.
UV-Sculpt is disabled.
I wanted to select a single vertex in order to select an edge loop.
The mesh has been created by adding a cylinder, then assign "Nothing" and then using the Solidify modifier.