Apparently two years ago, someone ran a static analysis tool named "Valgrind" against the source code to OpenSSL in the Debian Linux distribution. The Valgrind tool reported an issue with the OpenSSL package distributed by Debian, so the Debian team decided that they needed to fix this "security bug".
Unfortunately, the solution they chose to implement apparently removed all entropy from the OpenSSL random number generator. As the OpenSSL team comments "Had Debian [contributed the patches to the package maintainers], we (the OpenSSL Team) would have fallen about laughing, and once we had got our breath back, told them what a terrible idea this was."
And it IS a terrible idea. It means that for the past two years, all crypto done on Debian Linux distributions (and Debian derivatives like Ubuntu) has been done with a weak random number generator. While this might seem to be geeky and esoteric, it's not. It means that every cryptographic key that has been generated on a Debian or Ubuntu distribution needs to be recycled (after you pick up the fix). If you don't, any data that was encrypted with the weak RNG can be easily decrypted.
Bruce Schneier has long said that cryptography is too important to be left to amateurs (I'm not sure of the exact quote, so I'm using a paraphrase). That applies to all aspects of cryptography (including random number generators) - even tiny changes to algorithms can have profound effects on the security of the algorithm. He's right - it's just too easy to get this stuff wrong.
The good news is that there IS a fix for the problem, users of Debian or Ubuntu should read the advisory and take whatever actions are necessary to protect their data.