Why do I have problems revoking permissions on some tables with SQL Server?

A. A. This is a known bug in SQL Server 6.5 with tables that have 8n-1 columns. I.e. 7, 15, 22 etc.

To workaround it remove all entries from sysprotects and then re-grant permissions as necessary.

use <dbname>
go
exec sp_configure 'allow updates',1
go
reconfigure with override
go
delete sysprotects where id = object_id('<tblname>')
go
exec sp_configure 'allow updates',0
go
reconfigure with override
go