Ok, then what that tells me is that the data is corrupt and you are not able to clear it, and its stuck at a system level and the system thinks its full. The only way to fix that, is with a reset... but its not as bad as it sounds.
As long as you have a Google account synced to your device, your contacts, calendar, etc. will be re-synced to the device after you run the initial setup again as long as you sign in with the same Google/Gmail account. Any apps you have paid for, you can get back after you reset the device by opening the Market, pressing Menu on the phone and choosing "My Apps".
I recommend you go to http://google.com/contacts on your computer(with the same google account thats on the phone) then check all your contact groups to make sure the contacts are synced(if not, ask me about contact backup instructions).
As far as any data that is stored on the SD Card(images, music, etc.), it will not be erased. Only the phones internal memory is formatted.
If you need to know how to reset the phone, just let me know.
If you have any further questions or this solution does not resolve the issue, please feel free to let me know...
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