Doesn't sound correct. Assuming your source is 1080i60, why would you want to convert your frame rate before you create your master?
To change the frame rate, you need to create a new sequence, set to the frame rate and codec of your new media (assuming it's ProRes HQ 1920x1080 p24). Then copy and paste everything in your old timeline into that new timeline, then run through it, check for gaps and audio sync.
HOWEVER, from the information you gave, I'm not convinced that you are doing the
Right Thing?. If you shot DvcproHD 1080i60, you need to edit in 1080i60, then a frame rate conversion on the master if required (usually it's a standards conversion for PAL countries if you are working in NTSC rates). Also, you mentioned "render", which is horrible to convert frame rates.
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