It is possible the N900 corrupted the SD card. I could be mistaken about how the N900 works, but the moment the back cover is opened the SD card is made inaccessible and it doesn't seem like there any time for the card to be cleanly unmounted.

You can put the card into N900, open a terminal, get a root shell (I assume you have rootsh installed, if not then you'll need to install it), unmount the SD card with "umount /dev/mmcblk1p1", run a check with "dosfsck -aw /dev/mmcblk1p1", then wait a little while after it has finished just to be sure it has actually written any changes it has made, then you can take it out and try it in your Streak again.