why my phone suddenly cant read amy sd card?

[AC Question]

I left my phone off while charging coz it was battery emptied by my son. When I open my phone the display says "removed SD card". So I turn it off again, took it out and put it back again. But its still displays the same.. I borrowed my niece SD card and it displays the same.. But I didnt download or search any today.. Just my son played the farmville country scape and bubbu..
I borrowed another SD card and it still dont read but their SD cards are running quiet well in their phone.. I have an antivirus app on my phone..