ahh, okay folks, if you're on OS X, don't use ASDM-645-206.bin... 645 works fine tho so far.
i'm getting tired of correcting myself. So i set the ASA to use the asdm-645.bin instead of 645-206 (latest as of posting) asdm image and my already installed ASDM app on the macbook works fine and doesn't ask me to update. but if you need to actually INSTALL asdm (if you don't have it already installed) you can't seem to do that. i still get a 'page cannot be displayed' type message from Safari, Firefox and Chrome on my mac when i try to open HTTPS://ASA_IP_ADDRESS where i would usually install from.