In my version of Open Office, there are no shortcut keys to insert rows or columns. You can create shortcuts using Tools > Customise > Keyboard tab.
On that tab, in the box labelled 'Category' select 'Insert'. In the next box (labelled 'Function'), scroll down to 'Insert Columns', for example. In the top box labelled "Shortcut Keys," select a shortcut you wish to use. Press the button labelled 'Modify' and the name of the function you have allocated to the shortcut keys will appear in the box at the bottom right labelled 'Keys'. When you have finished allocating shortcuts, press 'OK'.
OpenOffice 3.3 on PCLinuxOS. There are 3 kinds of people: those who can count and those who can't.