I am now experiencing a similar situation with Win 7 pro.
As of the latest Mozilla Firefox update (ver. 50.1.0) and Adobe Flashplayer update (ver. 18.104.22.168) I can no longer sign-in to watch a TCM ON-DEMAND movie. Only TCM ON-DEMAND seems affected by these updates, everything else no problem.
I can use an earlier version of Mozilla and sign-in, but with the latest Flashplayer loaded I suddenly get very frequent "buffer-like" spining circles, and movie screen "black-outs". The Flash player crashes about 3 out of 4 attempts to watch an ON-DEMAND movie. And with the latest Mozilla update I can't even sign-in to watch anything ON-DEMAND.
Very bizarre. And way too typical of TCM.
you may have had an issue with the latest flash updates or shockwave. i have had this happen with my win7 prox64 machine. I used chrome for a bit and next time i went to try fire fox it worked ok again.. over the years with turner, i have experienced a few periods of no TCM that resolved with time. i did not find out whether it was turner ,adobe, both or firefox too.
my issue with the Mint 18 build I just did has not gone away over months , while the Mint 17 machine works just fine , and worked properly through the kernel updates 4.2.0-no need to change kernels beyond this currently. oh, well. lucky i do keep computers around for movies, streaming things. do not need brand new or high power to simply stream video, watch dvd, blu ray though 4k rendering may require higher power gpu for some video watching . i believe the tv can handle that if/when 4k streaming becomes standardized. but i am not there anyway and just guessing.