Sounds like the clutch is not fully disengaging. Volvo is
one of the few with fully synchronized reverse gear so it should
never grind (even if you are moving a bit). You could try bleeding
the clutch. I've done it and you do need to be careful because ANY
air in the line renders the clutch pedal useless (it will just fall
to the floor).

Was the transmission oil recently changed? You should use Volvo
specific gear oil if this is done (but tranny is sealed for life so
you should never have to replace it).

Volvo also offered a revised clutch spring that is supposed to
make it easier to shift. There was a technical service bulletin on
it. I posted some info on that here:

http://www.brickboard.com/AWD/?id=570427

Note the TSBs listed in the above posting may not apply to your year.
A dealer could check for you. If you get the spring get a copy of the
TSB since it has install directions.

Having said all that I have noticed that with 80K miles on my
98 S70 T5M that I do have to shift slower now and sometimes (rarely)
I grind 2nd to 3rd gear shifts (usually when I shift too fast).