I then tried to open a few audio files and I got the following error:
Windows Media Player cannot play the file because there might be a problem with your sound or video device. Try installing an updated device driver.
So, I uninstalled all of the Windows Security Updates, which solves the problem sometimes, but not always. If I completely reinstall my sound card, sometimes that works. Neither method on its own or together is consistant though.
I can't seem to find any reason for the problems. All I know is that it never happened before updating windows the other day.