For sure your mobile and your memory card is infected by a virus,might somebody send a bluetooth message to you or the virus comes from other memory card or your card has been plug into a computer which has a virus.this is a common problem of WD2 phones like 6600,3650 etc.
To fix this problem, scan your memory card to a computer which has an updated anti-virus installed.use a multi media card reader.after scanning and if detect any virus, erase it and install a mobile anti-virus application.
Download this application to your computer and install it on your mobile or memory card.MOBILE ANTI-VIRUS
On your phone,you need to Format or reset your phone to remove the virus on your phone memory.By doing this, type *#7370# on your home screen,a lock code will be ask then enter your code (if you change the code before)or the default code is 12345.this will reset you phone and back to its original settings.
Take note that if you format your phone,be sure all important files like contacts,photos is back up because it will erase everything after the process.
you must do the 2 method, if you disregard one of them,it will still give problem because they will infect both system on phone memory and the memory card system.
Hope this method helps. Thank you for visiting Fixya..