Range tool

I am not at my mac to check, but I guess this may be because you are selecting a range between two connected clips. Turn them into a storyline (select them and press Command-G) and then you should be able to select a range across them.

When you've made the selection like this

press ⌥ \ to top and tail the clip, remove the beginning and end.

If you want to remove just the beginning of the connected clip don't make a selection, just place the pointer with the skimmer from where you want to trim

and press ⌥ [

If you want to trim from the end move the skimmer and press ⌥ ]

What exactly are you doing? Are you dragging with the range tool like this from left to right?

You're right Luis. It's because they're connected clips.