For some reason, I can't seem to be able to access my gem vault.
I enter the bank, and I have the option to deposit or withdraw gold, but nothing about gems.
Has there been any change to the game to cause this?

Same here, cant deposit or withdraw gems right now, I'm sure Houko will fix it when she next comes to check up on us

I can see the deposit/withdraw options in the bank just fine. Are you by any chance not in Degolburg's bank? (for example, dragon isle's or any of the moon's)

It was definitely in Deg bank, and I tried several times.. but then later it seemed to have fixed itself. Weird.

Sometimes, you can be physically in Degolburg but still be in Dragon Isle (check the Fellow Inhabitants page to see where the game thinks you are). I'm trying to find all the places where this could happen...

I don't see how that could happen.
it happened to 3 different people at the same time, and I, at least, haven't been to Dragon Isle for at least a week before it happened.

Currently, I do not see how it is possible for this to occur under normal circumstances. If it happens again, please copy down the URL in the address bar of the bank page that does not have the gem options.

it has happened again
tai and I don't have any options but the basic withdraw/deposit/take out a loan/transfer money choices

the bank url is
http://iori.puuwa.net/bank.php?c=427-095003
and yes this is for the bank in degolburg

the mine and lumber yard have also disappeared

Actually, it's fixed for me now. For me, it seemed to be part of a bunch of different things that went weird earlier, like the lumber yard and the mines disappearing.

This seems to be related to a datacache bug whenever a module in the game is deactivated (any module). As yet I have not isolated the cause of the bug, but if it does happen, it will go back to normal once the cache is refreshed (which, I think, is 15 mins).