Did you make a new filesystem after you lost access to the files?
Let testdisk analyse your device with quickly, then hit enter and choose 'Deeper Search', afterwards let it show you the files and folders on the first partition with 'p' . Good luck!

At the end of a day, well, i think there are different series of the N900 around. There are rocksolid devices, where it really is difficult to get your file-system borked, and there is, ahem, yours and some others.... It is the same for overclocking.