Updated to Android V3.0. It won't let me change the date on tasks. I would change them. they would change back on their own. During edits it asks me to add a project to a task that used to have a project. I canceled out and I deleted 3.0. I pulled in my backed up version of 2.1.3 so I could function.
What is the fix?
You say 3.0, but we had a few update since that time, were you on 3.0 or were you on version 3.0.4? As there were many issues that were fixed in those updates?
Were you offline when trying to edit then tasks?
Play store does not show version number unless you expand the lowest arrow. It said 3.0 on top so I assumed it was 3.0. I just redownloaded and it seems to be working correctly now. You may want to move the actual version number up a bit higher for situations like this