Realmac and other developers advised customers to decline iCloud Drive by selecting "Not Now" from the pop-up that appears on their screens.
"DO NOT upgrade to iCloud Drive if you want to continue to use iCloud to sync Day One on devices running iOS 7, iOS 8, and OS X Mavericks," warned Bloom Built, the company behind the Day One digital journal and diary, said on its blog today.
Meanwhile, Dropbox alerted its customers of a different problem with iOS 8.
"We've discovered that Apple's new iOS 8 introduces a compatibility issue that may prevent Dropbox and Carousel from properly uploading your photos and videos," the company said on its blog. "This means that only the contents of your 'Recently Added' album will upload automatically." Other files added to Dropbox normally continued to sync.
Dropbox told users to refrain from deleting photos or videos from their devices "until you're sure that your stuff has backed up to Dropbox."
But by 3 p.m. ET, Dropbox said it had fixed the problem and had issued updates to its iOS apps. "We've resolved the iOS 8 compatibility issue. Please update your Dropbox and Carousel apps to get the fix," the firm said on Twitter.
The updated Dropbox app for iOS is available on the App Store.
Sign up for CIO Asia eNewsletters.