I've had issues with the select tool working intermittently. Right now it is not working. When I attempt to select a line, it responds "Choose second edge". When I try to use the parallel tool, it usually does nothing, but sometimes will consistently work an a single entity, but not on any others.
When you are asked to choose a second edge you have used "select window" and when you thought to have selected a line by clicking on it you have instead defined the first edge of the window. So you are asked for the second, opposite edge.
In most cases you don't necessarily have to use the dedicated selection tools, but during an operation just click on the entities when asked for (close the selection with "enter"). Or pull up a window around them before the operation.
The parallel command (offset) doesn't work on all kind of objects, for instance not on ellipses, splines and blocks.
If I have the parallel tool selected and approach a line (yep, just a plain old line) with the cursor I should get a preview of a parallel line. Sometimes I do, mostly I don't. If I have the trim tool selected, it says 'Select limiting entity', when I approach a line nothing happens. When I click the mouse, nothing!
Trim: When you select the limiting entity it just changes the colour, doesn't get dashed, maybe hard to notice. Then select the entity to be trimmed.
Parallel: You don't get a preview when just approaching a line, it has to be selected, either before triggering the "offset" command (then there will be a preview at once, without having to approach the line), or during the "offset" process. Is the proper distance set (not 0)?
Else I have no explanation for your troubles. Could it be a hardware problem (mouse)?