selection problems

For some reason when I'm in a command, I'm unable to select objects.

Example:
I want to trim a line. I click on the trim tool, which prompts me to select the limiting entity. I move my cursor into the drawing area and a small gray cross appears; I hover it over the limiting entity I want to select and click --> nothing happens.

Any ideas?

When you click the limiting entity it does not get dashed, it just gets darker. Then click the entity to be trimmed, and it happens.

Which version of LC do you use?

Can you try that on the development snapshot - (available there -  https://github.com/LibreCAD/LibreCAD/releases/tag/2.2.2_alpha-latest)?