SD card problem, card gets suddenly removed and later added- Sony Xperia X8

I am using xperia x8 version 2.1 update 1. Sometimes my phone creates problem with sd card i.e it automatically ejects stating *"sd card unexpectedly removed"* and after sometime it again shows *"sd card preparing"* and it works on. This distracts me to work in phone automatically the process gets delayed. I even tried by shutting down my phone, but the problem occurs.