I’m having exactly the same problem. The gem store is blank, all other tabs including the redeem a code are working fine (mostly). I’m running Mavericks on a 2011 MacBook Pro.
Last time this occurred (a few months back) I logged onto my Windows 7 PC and was able to buy gems. However, that requires me to patch the game which will take all night so I’m not sure yet if that will allow access.
I’m sure this must be a high priority for Anet as we can’t purchase their product until its resolved. I just want to make sure you’re aware it’s still happening.