Massive latency on Waves H-delay plugin (only)

Hi there. I just bought a brand new iMac (3.3GHz quad-core Intel Core i5 processor) and also bought the Waves Platinum Bundle. I used migration assistant to move over Logic to the new machine, then downloaded Waves Platinum onto the new machine (I hadn't yet installed it on my old macbook pro) - so a fresh install.

I've tried maybe 10 or so plugins from Platinum - and all is well, except for H-Delay. I inserted it on a guitar track, and initially it was fine (first play through). Then all of a sudden I started getting some extreme latency - or what I assume is latency. When I playback the track, the audio doesn't start playing until about 1/2 a second in. Same goes with having a guitar plugged in and playing real time - if the H-delay is inserted and active on the track - and I hit a note - it doesn't play back until about 1/2 a second later. I tried different buffer settings in Logic to no avail - and this shouldn't be an issue anyway - this is a powerful new iMac and no other plugs were on - just 1 track, 1 instance of H-delay. I tried some other delays and all of them are fine.

I did a reboot twice, same problem. And after one of the reboots, when I inserted the H-Delay, it initially had a question mark over the insert - which went away after I clicked it - but the delay/latency is still there. I can't for the life of me figure out what's wrong. Is this a Logic problem? Should I delete Logic and do a fresh install from the app store then re-add Waves?