I get err ';mem full.pls close application and try again'; in my nokia 5800. pls advice how to get rid of this.?

After each 3/4 hours my nokia 5800 (manufactured in april 2009) shows err ';Memory Full.Please Close some applications and try again';. This err comes while opening messages. Once this err comes most of the other application donot start at all.\r\nFor the time being I have to restart my mobile each time I get this err. I have more than 70 MB free phone memory.





Please advice what needs to be done.I get err ';mem full.pls close application and try again'; in my nokia 5800. pls advice how to get rid of this.?
Go to the nokia service center and get it repaired