by Wes Matchett.
Yes, I have considered that as well, but I only do server changes during breaks and over the summer. December was the last time any server changes were made.
After writing that last paragraph I decided to test a theory - to log in as one of the students from admin and change their theme. However, when I logged in and before I changed anything, I opened the class - and it was fine! So I tested another student (the other I could remember since I am at home now) and he is also ok. I will test the other student first thing in the morning.
This worries me almost as much as not being able to find a the source... a problem that comes and goes without an identified cause.
Thanks for your help. I will post back furthur developements.