You could try to re-flash the firmware of your mobile phone by using the Flasher software. To flash from the Windows (XP, Vista, or 7) command line:
1.Download and install the latest version of the Flasher from here.
2.Download the latest firmware (.bin) file for your region and save it to %ProgramFiles%\maemo\flasher-3.5\ (the default path), or wherever you installed the Flasher from here.
3.Ensure the battery is at least half full.
4.Unplug USB cable if present, and switch off the device.
5.Run the Flasher from the Start menu
6.This is an alternate to step 5, if you have already opened the Flasher, ignore this step. Open the Command Prompt (Start then Run or Windows Logo key + R) and type cmd then press Enter. Change the directory to where you installed the Flasher (TIP: Use the TAB key to auto-complete commands and file-names)
7.Hold the u key on the device keyboard and connect the USB cable at the same time. (TIP: Hold the u key until Windows has successfully installed the driver.)
8.Run the following command (TIP: Do not include '-R' if you are flashing EMMC as well, see below):
Replace RX-51_2009SE_2.2009.51-1_PR_COMBINED_MR0_ARM.bin with the firmware you wish to update. (Make sure you have downloaded the actual corresponding file.
flasher-3.5.exe -F RX-51_2009SE_2.2009.51-1_PR_COMBINED_MR0_ARM.bin -f -R
The flash will take approximately 2-5 minutes after which the N900 will reboot and display the Welcome Screen with Regional settings. After booting, you may use the backup utility to restore your settings.
Source here - Meamo