I was having the issue after upgrading to L9.1.7 as documented here: viewtopic.php?f=1&t=82495
Unchecking the offending auto mapped plug-ins in the Audio Units Manager stopped the crashing and rescanning process with each start up.
It's not uncommon for one DAW to be cranky with some plug-ins while another DAW does not.
Logic X 10.0.4 on both: i5 MBP 10.9, MacPro 1,1 10.7.5. Track 16, UAD 2 Quad Apollo & Satellite, K8, MachFive 3, HALion Sonic 2/ HALion 5, PSP, NF, LGX-SA, GI-20, JTV-59+Fishman Triple Play, MIDI Guitar app, SL Mk ll 25.