Doubled accents, another one appears even after hitting space

Hi,
I'm using the US - International keyboard layout and didn't have any
problems until now. When I type a ", then space, then another letter, another
" appears. For example:
""He walked."
"What I did was type one quotation mark, hit space, then type H. (As you
see, even after an enter another quotation mark is added, at the beginning of
the previous sentence.) This happens with all accents, such as ', ~, ^, etc.
I have no idea why it happens, but it's very annoying, so any help would be
much appreciated.