[ic] "Cannot merge metadata -- column(s) 'extended, default' is missing in table mv_metadata"

[Art]

Upgraded from 4.8.7 to 4.9.8 during a major server move.
Everything _seems_ to be working now, except it doesn't seem to be using bulk 
pricing even though it's all filled in as before, all data seems imported 
without too much trouble, but the main menu upon login shows:
UI update appears to have been done and metadata has not been updated for this 
catalog...
    Merge Metadata 

So, performing the Merge Metadata causes the following error message:
Merge run, UI version 4.9.8, metadata version 4.8.7
        Cannot merge metadata -- column(s) 'extended,default' is missing in 
table mv_metadata.
Items to merge

And that's it.
Sorry if I'm being dense on something obvious, but I haven't the slightest 
idea how to proceed. I'm a systems/network person, not a developer or dba 
type, and since it's a tiny company there's no budget for much else, so any 
help is appreciated.
Do I need to create some columns? Did I do something wrong during the upgrade?
Please advise.
Thank you,
-Art