multicam wi XDCAM EX needs render to view during edit

I'm doing a 3 camera multiclip edit with XDCAM EX 1080i/29.97, 35 mbs vbr, footage and when I put my multiclip on the timeline using safe rt/dynamic I get a red bar and it needs rendering to view. In unlimited RT/dynamic playback I get a yellow bar, but the quality is too poor to make edit decisions on focus etc..

I haven't done a multiclip for several months, but it seems that using DVCPRO HD, I didn't run into this problem. Am I missing something basic that would be obvious to anyone "with a clue"?

Machine is a quad core Mac Pro/Apple raid, 10 gigs ram & Kona 3 card.

thx...jw