Whenever I go to save a replay it says 'Unable to save replay'

Why does it do that? How do i fix it?

Don't use ?'s in the title or anything like that. You can use .'s But thats all i know about that problem

It means that the character (such as "abcd!!@#$%^&*":?>, etc") is not allowed to be used for that name.

You see, saving a replay is just like saving an image.
As you can notice, if you rename a file "?, etc", it will say "A file name can't contain these characters"....
So replay saving is just like file saving or renaming.