I've had a similar (probably worst) problem with Mystique Santorini.
Free cancellation (till april 30th) with 100% deposit charged at booking.
Canceled on april 20th but not received a reimburse....they wanna give me a 18 months voucher+10% value.
Other blablabla as others above...!

Why is (maybe) worst than yours?
1) the hotel is probably the top-end property in all marriott Greek portfolio. (well...not a big deal)
2) on their own website they say that clients can choose to keep the deposit in their sistem. If clients wanna have a refund they say they'll do it. But I couldn't choose!
3) if clients wanna keep the deposit in their system they give as advantage a +20% value.......but they give me only the half of what they promise!

Really disappointing!