iPhoto 8 freezes on startup, possibly due to Library data

I can't get iPhoto 8 to open any more on my iMac running Snow Leopard. The program starts up, shows an empty iPhoto window, and then the spinning wheel just spins and spins until I force quit.

I suspect that this is because something has gone wrong with the photos and data in the Library file. I say this because if I launch iPhoto while holding down the option key, and select an "empty" Library file with no data on it in my local hard drive, then iPhoto can open. But when I try to open iPhoto with my real Library that has all my photos on it on an external drive, it now is freezing as described above. Of note, my Mac crashed and rebooted while iPhoto was open, and then this startup problem began. This has happened to me in the past, but if I reboot the Mac then iPhoto seems to work fine again. That's not the case this time.

Also, in case this is important, my iPhoto library has grown to about 150GB in size. Could this be part of the problem? Is there a limit on how many photos or how much total data that iPhoto can handle?

Any advice to solve this would be greatly appreciated.