columns locked together

[Gregory Margo <gmargo pacbell net>]

I've gotten my tax spreadsheet into a funny state - some of the
columns cannot be individually selected, and several columns select as one.
For instance, column A is single, but selecting any of columns B-E
cause all four columns to be selected.
The actual groupings I see are: A-(B-C-D-E)-F-(G-H-I-J)-K

How can I get the columns split back up again?
(And how did I manage to get them locked together in the first place?)

thanks for your patience,
gm
(using Gnumeric-1.0.4)
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Gregory H. Margo
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