I'm not sure what's going on, but when I go to my bitcoin wallet's address book, my addresses are missing, and I cannot create a new one either. When I try to create a new one, it's prompting me for an address as well as a name for the address. Previously, the address field was grayed out and it would generate that on its own. My balance and transactions are valid, so it's not as if the whole program is not working, just the address book. Probably completely missing something here. Any ideas?
It sounds like Bitcoin-Qt. I'll describe the operation first (master). Go to the "receive coins" tab. When you press the "new address" button in the lower left, the dialog that comes up has a box for both label and address. However, the address box doesn't allow input (which is confusing). Input just a unique label and press OK. The dialog should go away and the newly created address will be highlighted back in the receive coins tab.
If this doesn't work and the receive coins doesn't show addresses you previously received payments at, it is likely that the wallet is corrupt, not able to read previous payment addresses. Starting bitcoin with the command-line option -salvagewallet will attempt to create a new wallet with recovered keys, but will remove the labels; this may have already happened automatically.