Yesterday Microsoft suspended automatic installations of KB937287, a servicing stack update required prior to installing Windows Vista SP1 and marked important.
Nick White made the announcement on the Windows Vista Team Blog, in which he stated: "Immediately after receiving reports of this error, we made the decision to temporarily suspend automatic distribution of the update to avoid further customer impact while we investigate possible causes." according to White, only a small amount of customers are affected and only in unique circumstances, he also went on to say that Microsoft are working to identify possible solutions and will make the update available again shortly after the issue has been addressed.
Microsoft has advised anyone who is affected by the issue to use System Restore or contact 1-866-PC-Safety for help troubleshooting.