brought with it a rather nasty bug that primarily affected non-mana using DPS including hunters, feral druids, rogues, and death knights. The client was disagreeing with the server on exactly how much haste refreshed the regeneration time of focus, energy, and runes, causing the client to report that certain resources were ready for use before they actually were, which then caused the player to press the button and the ability to not fire.
CM Bashiok has been keeping us up to date
on the status of the bug and just recently reported that it should be fixed via a hotfix that was applied late last night. You can read the full text of his post behind the break.
2/9- The Haste issue should now be resolved as of a hotfix that was applied late last night.
An apparent last-minute bug which was not found on the PTR before the patch was finalized has caused the client and server to disagree on the way haste affects resource generation. This bug will manifest itself in the UI showing a player they have enough resources to use an ability, but the server correctly prevents it as they in fact do not. A death knight for example might see a rune light up that isn't actually available so when they use the ability, it won't fire. A rogue may think they have enough energy to use Sinister Strike, but they can't actually afford it so when they push the button, they will get an error. This bug could affect rogues, death knights, hunters and Feral druids, because these characters all gain more resources from haste. It will also affect buffs that affect attack speed, such as Slice and Dice, Windfury, Icy Talons, and Hunting Party, but also attack speed lowering effects like Thunder Clap. We're currently working on a fix.