Hi,
I think i’m having the same problems as you, Ross.
I’ve just upgraded to AE 5.5 and am finding it frustrating slow.
(quad core intel xeon 2.66GHz, 8GB RAM, 10.6.7)
ram previews often just don’t work.
the system locks up completely during renders, so much so that AE seems to stall – making render times ridiculous.
Moving the payback head around results in the viewer going black so no scrubbing – annoying.
purging seems to do nothing i need to quit the app every so often just to get stuff to work.
feel like a major step backwards. again.
i fixed the problem with audio not always working or just slowing things down by randomly changing the audio hardware settings…