I am having the same problem. I'm using RM 7.5.5. When I try to connect to FamilySearch, two times out of three it will say that my password is incorrect and then when I back out of that screen all of RootsMagic is frozen. I have go into TaskManager to close it down and reload it. Everything is fine until I click the little blue icon next to a persons name that would normally bring up the FamilySearch box. Every once in a while I load RM and click that box and it logs me into FamilySearch with no problem, and then I transfer a few things, get out of that person and then try another person and it says my password is incorrect and then freezes RM.
I've tried uninstalling and redownloading a fresh install. I've tried different family files, it's the same thing.
I've deleted my virus scanning program and turned off my firewall and still the same thing. I'm using Windows 10
I went ahead and reset my password and did the file reset thing again and this time I got an error message "Family Search can not process your request". I can sign onto FamilySearch with my new password.
Edit: After the error message I shut everything down and restarted my computer and tried again and it seems to be working for now but I've had it working before only to return to the freezing, so I'll check in again tomorrow.