It sounds like a residual effect of formerly using it as part of Mobile.me
http://support.apple.com/kb/TS4291 Look at the fourth instance for your case.
Try stopping it in iPhoto preferences > Sharing and deselect Share my Photos. That may stop it from connecting to the iDisk server.
Not having used this service, I'm not sure how effective is the advice I have given, but it won't hurt anything to try it.
Message was edited by: roam
I had the same thing happening. When I looked at my iPhoto preferences, under accounts, my email account was still listed as a MobileMe account. I am using the same email address, so it didn't occur to me to change it. I deleted that email account by highlighting it, and clicking the minus key, then hit the plus key, and established the same address/password as an iCloud account. It doesn't look for MobileMe anymore.