This happened to me as well, here's the details.
Prepatch problems:
Guild Bank would continuously display "Retrieving items" without actually doing so. Tested at eight minutes of "Retrieving items" before applying the fix. The fix is to press Y and switch between guild banks until it succeeds in loading, or exit and reenter the bank.
Postpatch Problems:
Guild bank continuously displayed "Retrieving items" without actually doing so. Allowed it to attempt to display the items for five minutes and attempted to apply the aforementioned fix. Issue did not resolve. Tried again. Did not resolve. Displayed the ability to withdraw gold from the bank, but items did not populate. Logged out and logged back in. Same issue. Prior fix displayed the ability to withdraw gold again. Selected 'Withdraw Gold'. Interface would only allow 9 gold to be withdrawn at a time. Same with depositing gold. Deposited two items, items did not populate. Deposit screen shows player inventory numbers instead of guild inventory numbers (i.e. --/130 instead of --/500). Logged out and logged in as a different character. Fix worked for the guild bank. Logged back into the other character. Issue resolved.
Being away from the bank for an extended period of time causes this issue to repeat.