I can’t reproduce any of your issues on 7.10 RC. Can you please try it in that version also?
And can you check both suitecrm.log and php_errors.log to see any messages there when it fails?
If it still fails in 7.10 RC, please list exact steps to reproduce: which module, which view, which changes, which button to press. Maybe the issue is specific to only some part of the app, and it helps if I’m trying to do exactly the same steps as you.