Howard Miller

Site administration -> Appearance -> Theme settings

There's an option to set the theme for an individual user, a course or even modify the URL to specify the theme.

What happens if you switch to the Boost theme?

Marcus is correct that you should probably do more to investigate the underlying issue.

However, I think we can probably assume that it's some sort of resource issue. When you create 300 and then sleep - did you guess the sleep time or actually do something to see how long it takes to create those courses? I suspect that creating 300 courses could take quite a long time.

If you mean Manager as in the role Manager, why do you have a Manager enrolled in a course?

Yes.