What does this error mean?

[thorvald]

   siac host announce
   Could not announce host: consensus conflict: transaction spends a nonexisting siacoin output.

In the wallet I have a Pending: -0.03000000000020009 S

[in-cred-u-lous]

You need funds in your wallet to announce yourself as host, and pay collaterals when storage contracts are formed. The amount required depends on the total storage you provide on the network. As a rule of thumb:

If using the defaults for collateral, you're going to need between 50,000 and 100,000 siacoins per terabyte you are offering to the network which will be used as collateral.

Source: http://blog.sia.tech/2016/05/26/how-to-run-a-host-on-sia/

[jordan]

The error I get when attempting to announce with no funds is

$ siac host announce
Could not announce host: insufficient balance

I remember encountering the error you got once, but I forgot how it happened. Pinging @Taek to see if he knows.

[Taek]

The wallet occasionally gets confused and tries to spend an output that it has already spent. I'm not sure where the bug is. It will clear/resolve itself after a day.