What exactly am I deleting with those entries?
Information about unspent transaction outputs got out of sync with blockchain because one of wallet transactions wasn't accepted by the network.
Wallet file is an sqlite database, you can use sqlite3 or sqlitebrowser to open it. If you delete contents of coin_data and coin_spends tables, they will be populating according information about unspent outputs from blockchain.info. (It is an equivalent of `bitcoind -rescan`.) You might need to click 'update' twice until it shows right numbers.
Of course, there is some bug in chromawallet which caused this, I'm investigating...
PS: trying to create a new receive address on the receive tab doesn't appear to work either. Nothing happens when you try to do so.
Yep, that page isn't working properly. It creates addresses, but they aren't displayed.