Windows phone 7 Calendar reminders not working

[WPCentral Question]

Previously I would enter in events to my calendar on my phone and a reminder would come up with a sound. But lately this had just stopped working and it's really frustrating. I have reminders set to appear 15 mins before the task, it is definitely set to on. If I happen to be using my computer a reminder will come up in the corner 15 mins beforehand. This was always there. How can I fix this so the reminders come up on my phone again?

 

[J Kul]

My Windows 7 Calendar is not opening. I click the calendar, the windows d o a cute little slid then right back to the icons. Anyone please assist??!!