Update The Ubuntu 10.04 release candidate contains a "major" X-Server memory leakage bug that "causes the computer to get slower and slower over time."
According to a bug report, the problem can cause system instability after "a day or two uptime" - depending on memory quantity and usage. Developers have proposed a fix, but it's still under test.
Ubuntu 10.04 - known as "Lucid Lynx" - is scheduled for official release on Thursday, April 29.
The bug is related to GLX (Open GL graphics system) patches that Ubuntu took from Debian to remain in sync with the distro. Debian has dropped the patches, but Ubuntu developers are still debating whether this is the best course of action.
"These GLX patches were produced by RedHat and incorporated into Debian. They were not brought in due to Ubuntu-specific requirements and thus it is believed dropping these patches would not impact any of Lucid's development goals. The one risk to be mindful of is if any userspace applications have come to depend on the newer GLX functionality," reads a wiki describing the bug.
The wiki says that it does not affect graphics cards that use proprietary drivers. It's specific to the GLX module used by X.org's open DRI2 drivers. Intel cards, the wiki says, will be affected, because they always used DRI2. ®
A fix for the bug has now been released.
A tip of the hat to The H.