I have spent months with this problem and FINALLY found out the relatively simple culprit and solution after talking with very helpful apple support people by phone (free live phone support is apparently available after upgrading to Mavericks).
The problem wasn't with iphoto. The problem was not having enough RAM to allow iphoto to do its thing. When plugging in my phone to import photos, it pushed my RAM capacity past its limit, which caused the endless spinning wheel and the computer freezing. In particular, scrolling through iphone thumbnails seemed to trigger the crashing.
To determine if this applies to you, you can open the Activity Monitor utility and click Memory tab at the top and then look at Memory Used -- if the amount of Memory Used is anywhere close to Physical Memory (available), then RAM could be the problem.
My IMac is only a few years old and came with 4GB RAM standard, but that apparently isn't enough nowadays unless you close everything else. Skype and Itunes were opening automatically and running in the background, eating up lots of memory. Obviously you can try and manage RAM by stopping those from opening automatically, etc., but regardless, I'm going to purchase more RAM.
