When I apply conditional tags to a table row or column in FM, it displays a message 'select complete rows before applying conditional tags FrameMaker'. FYI, I'm using FM 9. Thanks!
To build upon what Matt said, you can only conditionalize entire rows, not parts of rows or individual cells. You can conditionalize the content within an individual cell, but not an individual cell itself. Definitely a limitation (in my opinion), but there are ways to work around it depending on the needs of your documentation. For instance, if you need to hide just one column in a table, create a version of the table with the column and another version without the column, and tag the table anchors with the respective condtions.