The psets have been rearranged a bit. The c programs that used to run through pset 5 are now psets 1 through 4, so yes, some shuffling has occurred. Speller is definitely pset4 now.
I would suggest that you move all your completed work to an archive directory, put your in-progress work on Speller in a new pset4 directiry and proceed from there.
I had the same problem. What worked for me was to clear cookies browsing history etc.. and then use incognito mode (ctrl+shift+n). Strangely this didn't work in just incognito mode I also needed to clear cookies/history.
Failing that switching to another browser worked for me. I'm on a linux system and I didn't have the same problems using Chromium.