Hi Eric, thank you very much for your response. I have done what you have suggested, and iphoto seems to be functioning normally.
I have switched time machine off as I wish to upgrade to yosemite, and I gather that this is the right thing to do? Maybe not?
I wonder if I could trouble you with another question. I am tangled up by the fact that I have two apple ID's (entirely accidental) - one of which is now an unuseable email address which is on my ipad - and I want to synch my ipad to the imac eventually. So, with icloud, do I have to set up an icloud as soon as I download yosemite, or will it allow me to wait.... as I was thinking of setting up a secure email but I can't do that with my existing safari browser.
Also, does icloud allow you to use it for certain files only, for example, I don't want all my photos in icloud, I just want to synch things I write on the ipad to the imac. Is this going to be possible?
If I use my second ID to download yosemite, I am stuck with that in all other aspects of it.
I'm sorry to barrage you with questions, and will understand entirely if you don't have time to answer them....I'm sure I will nut it all out eventually. I'm sure I sound very confused about all this I guess that's because I am.......
Many thanks and best wishes.