Media pro crashing on light table

Hi,
I've created my catalogues in Media Pro but every time I try to show more than one high res image on the light panel the programme get stuck.
It is fine with low res jpegs but anything high res, raw, jpeg or tiff, it loads one and then gets stuck whilst 'preparing image' on next….sometimes will get going again after 20 seconds or so of loading but of course this is far from usable.
Any suggestions?
Using latest version on Mac with OSx10.74

Thanks.