To reproduce:
1. Create a new project and include two slashes instead of one in the location of the project
2. Notice the errors about failing to move files
3. After going through the errors you get a Fatal Error about a changed working directory and the only option is to quit

The project actually generates a valid directory, but unity still tries to access the one with two slashes.

If you are not using the welcome screen this issue will cause a crash on startup. The workaround is to press alt while starting unity or to rename the generated directory