I could be wrong, but a while back (in beta 1.0) they were increasing the number of players that could be in any given instance of an area at a time because we would be right next to each other, and then spontaneously despawn into separate instances. I'm pretty sure that the limit has been hugely increased since then, but it might still be possible that the area you're in is "full". What you could try doing is:
- Ensure that you're both friends in the "Friends and Private Groups" screen.
- Ensure that you're both in the same system (for instance, you're both at Aulin system's Aulin Enterprise starport).
- Both of you, without having another system targeted (by way of the galaxy map or the navigation panel on your left), supercruise.
- Drop your speed as low as it will go while in supercruise, instruct your friend to do the same, and see if you can find each other right there. Pick a target that's 100+ Ls away and head towards it slowly.
If you're not seeing each other there, I'm not sure what the problem is, so it wouldn't hurt to ticket it. I mostly play in a private group though (check out the Groups Discussion forum one level up from this one), so my experience in Open Play is a bit on the low side.
Best of luck!