content of /opt gone after kernel upgrade

I upgraded from KDE 4.24 to 4.31 and upgraded my kernels .
After rebooting, most of my GRUB entries would not start my system, while only one did (the but even though the YAST partitioner says /dev/sdb1 is 2GB (/dev/sdb1 is mounted on /opt), a df -h says that /opt is 61MB!
So everything that was on /opt is gone: no more k3b, no more Google Earth, and Open Office crashes everytime I ask it to save!

A Repair System with the 11.1 DVD did not cut it.
Mounting /dev/sdb1 somewhere else does not fix the problem: it’s still 61MB (even though fdisk says its 2220MB).

Here’s the line for that partition in /etc/fstab:
/dev/disk/by-id/ata-Maxtor_6Y080M0_Y21XC3DC-part1 /opt ext3 defaults 1 2

What can I do? I really need OpenOffice to work.