Weird, now I've gotten a bit of a technical issue.
I had no problem reading pokemon from my retail Heart Gold to my flashed Platinum.
Just tonight I've been trying to trade. Both trainers are in the trainer room, just fine. Then when I go next to one and press "A", I get a blue screen and a "A communication error has occured." message. Heart Gold goes back to the title screen, and Platinum refreshes the Union Room.
I just tried battling between the two, and it worked fine.
Weird, considering this worked just a few days ago.
I've reset both. Switched DSes. Updated to the latest firmware.
Any suggestions?