Hi Kathleen,
It sounds like in question one that perhaps you have a large file that is trying to upload?
In the second question you can safely uninstall any version of Muse as long as you don't delete the .muse files (Your site files). To be safe you can always back up your .muse files to a flash disk or second drive as a back up.
The only thing you can't do is if you opened a site in Muse CC 2014 you can no longer open it in the older Muse CC version.
