I can’t speak for the OP, but I’ve been getting this message for months, since the start of the year. The only way for me to access my client is to install 8.5.0. 8.5.1 alone or with any of the Fix Packs gives the error and refuses to start, on any OS, either 32-bit or 64-bit. There is something else going on. I’d really like to figure out how to fix it. I’m to the point that I may need to create a new account, which will be really annoying, but nothing else seems to work.