This could be due to the other issues including server lag, but I want to see if anyone else is having this problem.
After killing mobs, some of the items will not go into my inventory… Even from boss fights! 
Also, I was experiencing issues using my EXP cards that I received as Quest rewards. I right click and nothing happened.
I decided to log out and go back into game but had issues due to full channels. When I finally got back in, I could us EXP cards but still had troubles retrieving items.
This was within the first 2 hours of servers being up. Suggestions??