Opera font issue: Default font will not change

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https://bbs.archlinux.org – I noticed that every page I visit from Opera except this archlinux website has this horrible monospaced font displayed. I went to the font settings in Opera and switched defaults to sans serif fonts but still this monospaced font is everywhere. I checked author mode and user mode and each mode displays the same font. Firefox and Chromium don't have this problem, however, I did notice that when I play a youtube video or use something with flash player the font inside the video frame is the exact same font as Opera's font. Here is a screenshot: http://imageshack.us/photo/my-images/155/ (HowTos)