Hi @fredgenius,
Thanks for posting and welcome to the Fusion community!
I'm sorry to hear about these error messages you are seeing! This issue seems to pop up every now and then and as such, we have a great article linked here that provides some possible solutions for this. Could you try working through each of the solutions to see if that causes those messages to disappear? Before working through that article though, I would back up your local cache.
To do this, navigate to the below directory on your machine:
%localappdata%/Autodesk/Autodesk Fusion 360/*UNIQUE_ID*/W.login
I would just like to note that there will be no folder called *UNIQUE_ID* so you will not be able to copy/paste that into a Windows Explorer window. The unique ID is an alphanumeric string that is tied to your Autodesk account. For instance, my unique ID is WAPSJRUV92MF. It may be easier to navigate there manually.
Regardless, within that W.login folder, there will be a folder called "F". This is your local cache. You should put a copy of this on your desktop or another easily accessible location on your machine.
Once you work through each solution, I would go through your projects to make sure that all of your designs are there and are the most current version. If anything is out of sync, the design should still be in the copy of your local cache, and you can use "File > New Design From File" to get that version back. The only caveat with this is that you would lose the version history of that design.
I hope this helps! Please let me know if you have any questions or concerns - I am always happy to lend a hand!
Cheers,