I noticed on one of my systems running Debian Linux, some fonts where not displayed correctly (or not at all) when viewing pages using Flash.
This page led me to a solution for this problem. In my case, I only needed to install the gsfonts-x11 package. Now Flash appears to be working correctly.
The My Yahoo! “Today” module doesn’t display properly on my Ubuntu system. I think I do have gsfonts-x11 installed though. Does this happen for you?