iphoto 11 unusable..can I reinstall it?

Hi..I am having all kinds of issues with iphoto11. It simply doesn't respond any more and when it does, it is beyond slow. It is unusable. I gave about 200 gb worth of pictures in it. I have tried rebuilding the library but nothing changes..iPhoto 11 loads ok but the program it's self responds so slowly it is pretty much useless now.

What can I do to fix this?

My Mac specs are an iMac desktop running OS X 10.7.5
processor 2.66 Ghz Intel Core 5
Memory 16 Gb 1067 Mhz DDR3


any help would be greatly appreciated!