[mythtvnz] Storage drive won't mount

[Paulgir]

I had a power cut here about an hour ago and when the system rebooted I  
got a message: problem mounting /var/lib/mythtv
I have /var/lib/mythtv on a 1TB drive.And the OS on a 160 GB drive.
The drive is ok according to the disk utility.SMART data is good ran  
benchmark sucessfully.
sudo mount /dev/sdb1 /var/lib/mythtv gives a wrong fs error.fstab looks  
fine.

Any suggestions what to do?
Or how to temporarily revert to /var/lib mythtv on sda1?
I tried sudo umount /var/lib/mythtv but it tells me /var/lib/mythtv is not  
mounted   -of course.
Actually I think it has reverted by itself because it is recording to some  
directory.
Any ideas how to get my 1TB drive mounting again?

Paul