Hi @hartleg! Thanks for trying the beta and reporting this.
I haven't heard or seen anything like this before. I am not sure what is happening exactly. Did you have the old version of WP Tiles installed before you activated the beta?
I understand that your 'Edit Post' and 'Edit Page' are not working - are the pages loading apart from the editor? If so, can you check your your error console as described below:
In FireFox or Chrome: Open the page and right-click anywhere on the page. Select Inspect Element. In the panel that opens, go to 'Console'. Reload the page, and check for any errors coming up (in red).
Please report any errors back here if you see any.
If all that comes up blank, please let me know so we can delve further into fault finding!