They're hiding. You need to widen the Source Monitor's panel for them to be visible.
I thought CS4 did it differently, Eddie, with individual buttons for each.
Ann and Eddie,
I see the icons you (Ann) have boxed in the wider screen shot you sent. Thanks for going to the trouble. It seems those icons can be only used for drag and drop -- at least that is all I have been able to do with them. If one wants to use the insert and overlay keys on the keyboard for audio only or video only there may not be a solution in CS4. When using the comma and period keys the video and audio are both inserted or over-layed. It was easy with a specific clickable icon below the picture in the source window in the 1.5 and 2.0 versions.
If you only want the video you select V in the timeline and disable A1 and v.v.
AAAHH HAA. Of course. Thank you very much. I was fixated on the old 2.0
way. I really appreciate it.