Here are the steps
Running Mac OS 10.9.5 on a Macbook Air 13"
I had a previous beta version of Renoise installed (I think it was beta 5 but it may be 4)
I deleted renoise_reg from the applications directory
I downloaded Renoise RC1 64 bits and installed it
it crashed during the first startup while looking for VSTs. Looking at the window, it seems it crashed while looking for Synth1 32 bits.
EDIT : Sorry, restarting Renoise, it seems it comes from TAL Bassline 101 VST 32 bits