Why is Safari 5.1.10 asking to use the login keychain?

Safari has started to ask to use the login keychain suddenly, and when I try to cancel the pop-up box, it just pops back up immediately, effectively locking up Safari so I can't use it until I Force Quit and re-launch it. Then it will work as normal for a bit until eventually when I wake it from sleep it one time it will start asking for it again.

I don't want to give it access to the login keychain without knowing WHY it's suddenly started asking for it, as I have all preferences that might need it turned off, like the option to remember passwords or auto-fill form fields- all of that's turned off, and I don't want it to access anything security-related.

Any help would be appreciated.