Hi there.
Recently I have been working a lot on one map and it hasn't come to my attention until now that I am unable to create or open another project. I have recently joined the workshop beta and I am running Steam Indie Edition. I attached a video that shows the behavior.
I am not sure what to send to you as none of my projects except for one work but let me know if you need anything and I will send it your way.
--video
https://www.youtube.com/watch?v=iBw2hCEQ0iM