Remember the iOS 4 alarm bug that is affecting European users on Monday as well as Australia, New Zealand users in September? Looks like there is no fixes coming before November 7th, when North America is ending their daylight saving time. Apple has issued a support document advising users to handle the alarm bug manually.
The bug, according to Apple: “In some regions, shortly before or after the daylight saving time (DST) change, repeating alarms created in the Clock app may work incorrectly.”.
To resolve this behavior for existing alarms, set the repeat interval to Never. You will need to reset these alarms for each day you need them. After November 7th, 2010, you can set your alarms to repeat again.