Nokia 8310 - Snooze function gone wrong

I've had my 8310 for quite a while now, and it's pretty much turned into an alarm clock which occaisonally recieves calls.

Anyway, I set my alarm every morning, it goes off, I push snooze. five minutes later, it goes off again. It's the way the function has always worked on my phone.

This morning however it went off, I pushed snooze, and 20 minutes later the alarm goes off again. And I've no idea why

I've looked about through all the menu's and settings, and I see nothing that could have changed my 'snooze timer'. Is there something I musta pressed or has the phone just gone dicky?

Also, i just tested it again, and this time after the alarm had gone off and I psuhed snooze, the alarm went off again after 10 minutes.

So before it was 5 minutes, then it went to 20, and again without me altering any settings what so ever, it's down to 10.

Any idea on how to fix this?

have a look at the www.nokia.co.uk and look up ur phone there, they will have FAQs that mite help but if that doesnt let me know