Hi Andrew,
Yep, the "click on a whole rest to highlight it" does not work, but there is a workaround
1. Use Region Select, and select the measure(s) with the whole rest(s).
2. Then use Region/Convert selection to rests - the whole rest(s) will now be selected.
And just to avoid any further frustration, you can't delete rests, but you can hide them (it's the last button on the right of the Rests tool bar).
(It's a fine distinction, because our products are sort of like hybrid sequencer/notation programs, and knowing when not to play a note (rest) is as important as knowing when to play a note
)
ttfn,
Sherry