When I open a file in vim, lets call it 'file1.rb', this file opens normally with ruby syntax highlighting and no problems up to this point.
When I open 'file2.rb' in a new buffer, it turns both of the buffers into
Vim has a builtin command to disable diff mode,
*:diffo* *:diffoff* :diffo[ff] Switch off diff mode for the current window. Resets related options also when 'diff' was not set.
If you just want a quick fix, you can do this whenever you open a split, or even make a mapping or autocmd to make it easier. Perhaps something like
autocmd BufNew * diffoff
But this is definitely not the ideal fix.
There's still the issue of what causes it. A quick glance through your
.vimrc shows lots of plugins, but I don't see anything in particular that would cause it. I'm 90% sure the issue is from one of the plugins, so I would start there as you're looking for the problem. Also, this post over on the dedicated vim site will help you a lot: