Are you using mass memory for storing messages or phone memory?
If you are using memory card then delete "1000484b"
If still the problem persists then you will have to do some resets around.
Before perfoming this please take a backup of your data.
Factory defaults-
Type *#7780# on your standby screen.
This will reset all your setting to default factory settings. User data wont be affected.
Soft reset-
Type *#7370#
This will reset the phone as well delete user data. Use when want to format the phone.
If none of these worked then you might want to do a hard reset.
For this you have to-
1. Switch off the phone.
2. Hold down the following three buttons: Green (the call answer button), * button, and '3' button.( Just in case of N78 it will be the multimedia key the small silver key on right side & for Nokia 5800XM - use the following buttons to do a hard reset, GREEN/RED/CAMERA keys pressed all at once on power up. this will only work on 5800's that have firmware version 20... and up. For Nokia N97 is SHIFT /SPACE BAR / BACKSPACE. )
3. While holding these buttons, hold the power button to switch on the phone.
4. Release the buttons when the phone shows the nokia hands logo or shows other signs of life like the language selection screen.
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Currently using N82 and 5230. Next would be N?