Looks like your regions or tracks are grouped - thats normally the reason for that symbol.
At some point you might have hit Ctrl+G with some of the regions selected.
Open the mixer, and check that the channels aren't linked there by right clicking on them - if they are linked it should say 'control link' in the right click drop down. If that doesn't appear then all is well.
If the channels aren't linked in the mixer, then you should be able to use Ctrl+U to ungroup the selected regions.