The OS X 10.7.4 update introduces a bug with some Mac Pros, where a strange dialog box may be displayed upon each reboot containing the text keyApplicationTitle and keyWarningOptimalInfo. This dialog box includes a little picture of a Mac Pro, and the continue button is labeled KeyOKButton.
It has been found that this bug is related to Apple Memory Slot Utility, and appears to be just an annoyance, requiring you to close the dialog box each time you reboot. One workaround to prevent it from opening is to remove Memory Slot Utility from /System/Library/CoreServices, but then you won’t be alerted to changes in your memory configuration. Apple is aware of this issue.