If your website presents ("is stuck in") pset7 after you start apache for pset8, do a ctrl-F5 in the browser, that will reload the correct website.
(author's note: after rereading the question I realized the above may be the real problem, however since I already typed the below.....:)
There seems to be a bug in /etc/profile.d/ide50.sh that is causing this ...
So, while I still do not know what happened nor do I understand the solution. I found that another CS50x student had the same problem and posted about it on the Cloud9 community boards here.
The 'solution' post reads thus:
Hi, problem appears to have resolved using echo >
~/lib/apache2/log/error.log. I have access again
And I typed into the terminal: