Yep, I had the same problems: Wriring to file failed. I ended up submitting my assignment late (04 May)as I was in the remote area where i could not get any assignment box. i had to write a letter to motivate why it was late, hope they accept it.
Yep, had the same problem at around 15h00 and sent off a mail to the assignments email address. Wound up having to print out the assignment and then go off and find an assignment box as I take it that everyone was off for the long weekend.
Have another assignment due tomorrow which I tried to submit earlier today and now SOL tells me that I have an invalid student number and I can't even log in.