Unmountable EXT4 Logical VOlume

[Tobias Vinteus]

Hi, I recently installed Fedora 10 and converted my Ext3root partition to
Ext4 ackording to the Ext4 HOWTO. Now the volume cannot be mounted, or
even seen, as no devices show up - only the physical (/dev/sda7). LVM
shows the presence of the volume group and it's logical volumes. vgmknodes
doesn't have any effect.

I'm thinking I could somehow reverse the test_fs flag, or do an e2fsck,
provided that I know the offset of the superblock. 
Could someone kindly assist me here? Can I still save dthe day? :-)

Kind regards,
Tobias