I wanted to format my communicator becuase I don't have much memory in the device. but when I tried the "shift+F" after I remove the battery, I got the format interface, then I clicked on format and it did nothing, it continue to load the operating system !!!
I even tried to format it from the PC, I get some errors about unabling to proceed with formatting.
I uninstalled all third party's software to fix this problem but nothing worked.
any help would be great
MMX
On bootup press CTRL+SHIFT+F
this will work 
Didn't work either
(Backup any files you want to keep.)
Take out the battery.
Put the battery back in.
As soon as you've replaced the battery, open the lid and keep press the shortcut buttons mentioned above - keep pressing them untill the format screen comes up! And press them all at the same time ie; together. You should get the format screencoming up, and select 'Format'. If you get the Nokia logo start screen you're too late...Try again.
Last time i also face the same problems.When i try to format my device,its doesn't work when i press SHIFT n F...But after that,i take out my MMC card and try again and its work!So,maybe you should try to take out your MMC card before you want to format your device.Hope this can solve your problem.