I was frustrated for quite some time. If you have a Bandwidth Limit Exceeded error every time you try to do anything with wallets or posts etc then here is how to resolve that.
Just go to Buy Steem - under the menu in the three line menu on rightmost side of top bar.
Then once there send like 0.001 BTC or whatever (say $10) to buy Steem Power (not normal steemit because you won't be able to power it up without steem power already).
Send it your own name, which is your address and that should already show in the "your receive address".
If someone else can send you Steem Power - give them your address as shown there.
Once you have steem power again you won't have the Bandwidth Limit Exceeded.
The idea seems to be that spammers will run out of steem power and then they won't be able to keep spamming. Anti-spam is actually the original idea behind "Proof of Work" as implemented in Bitcoin and many other cryptocurrencies.